Some of these have already been covered, but I'll reiterate.
AW Features:
- Free building, no need to buy land, just plop an object down and the "land is yours"
- Ability to build in ALL directions, up, down, left, right. By this I mean, you can build above, or even *underground* something we can not do in SL currently. (however this is due to AW's lack of real physics)
- "Running" in AW is much faster. Probably somewhere around 3-5x's the speed of SL's running. This allows you to cover large distances in a smaller amount of time. (be sure to hold down Shift though while you do this so you don't keep running into stuff). Note: Not sure if running is disable-able in worlds, I forget and I'm too lazy to check my own.

- Worlds can be much larger in size than Sims. AlphaWorld, the main building world in ActiveWorlds is quoted to be almost the size of California. Worlds can be actualy *any* size, large or small.
- Worlds can be compeletely customized, everything from sky boxes, "physics", water, land, objects, avatars, etc. can be customized.
- Like SL Sims, worlds can have ratings and be restricted to users. However AW takes it a step further and allows you to specify what exactly users can do, either by "anyone", or by specifing who can do what specificly, i.e. "this user can build, and kick out users, but can't change world settings" or "all users can build, but only this user can kick out users".
- You can select what worlds you see based on ratings, i.e. I could select not to see any worlds with a rating of PG-13 or above (AW uses the standard movie rating system, G - X). I could even set a password to be entered in order to change the rating setting.
- Differntly powered users text appears differently. I.e. If I have the power to kick users out of a world, or have "speaker" rights, my text appears in bold, a normal users text appears in regular, and "tourists" (trial users, users who are not paying members) appear in greyish text. This makes it alot easier for Town Halls as the main speaker can "go bold" to make their text stand out.
- Worlds can have "welcome messages", and world announcements.
- Custom uploading of objects possible, allowing you to pre-model objects/avatars and upload them to your own world.
- Chat Logs can easily be saved by checking/unchecking an option in your prefences. URL's in chat are clickable and can launch your default browser or a built in browser (uses IE of course).
- Individual settings for people on your Contacts list. I.e. I could set myself to never be visibly online to a certain user, or dissallow a user to see what world I curently am in, or allow only one user to see what world I am in.
- Can set an offline mode.
- Using a system of "Citizen Numbers" (simular to ICQ numbers), you can freely change your name to annything and everything will update to reflect this, i.e. all the objects built in world by you will change the name to your new name (however your cit# is still displayed on the object), and also if you're on someones contact list, it will reflect the change. This can be confusing, but is still nice. It cannot be used for abuse as you can easily obtain anyones cit# (simular to Avatar-UUID Keys in SL) using bots etc.
- Different video modes. You can run AW in Direct3D, OpenGL, or Software mode.
- NPC's. Bots use Avatar's to represent themselves, which easily allows you to create NPC's. Bots names appear as: [OzSpade] where as my name would appear as: OzSpade to distinguish. Bot's names also display their owners Cit# next to their name, i.e.: [OzSpade] (331155).
- Ability to "skip" back and forth from your current teleport location to your previous. i.e. I can teleport to WorldA, then teleport to WorldB, then hit the "Back" button and teleport back to WorldA, and then I can hit the "Forward" button and teleport to WorldB again.
- Can set your home in any world, at any position, if the world allows it.
- Chat allows you to identify new messages from "scroll back", so if you scroll up, then scroll back down it tells you which messages are new from that time.
- Right clicking a name in the Chat window gives you the same options as right clicking their avatar, i.e. Telegram, view profile options, listing of Citnumber, etc.
- Swimming animations and different behavior when underwater.
- Total Time Online in your user preferences (only you can see it).
- Telegramming, AW's IM system works simular to SL's, It is sent instantly, however if the user is not online it is saved for them for when they do come on and they are then informed they have a Telegram waiting for them. Via GUI you then check your telegrams which shows the sender and the date of each telegram. You can then click to see the message. Or if you are online it is sent instantly. Now, whats different than SL's system is that Telegrams are saved untill you delete them, so you can keep telegrams in your list untill you wish (or untill you reach the limit, then you must delete some before more can be stored I think).
- Saving of direct coordinate teleports. If the world allows it you can save a direct teleport to any coordinate in a world.
- Worlds list, lists the current worlds (you can select which worlds you want to see, by rating or by public/private settings), AND you can see how many worlds AND how many users are currently online and in each world. (Something I'd love to see in SL)
- VRT, Virtual Reality Time, basicly a universal time to arrange meetings based on. (SL just uses PST currently). VRT is 2 hours ahead of EST and has the same 24 hour span as regular hours, presented in 12 hour form, not military 24.
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AW Bugs/NonFeatures:
- No custom avatars. There is no way to create your own avatar to always have and use in every world. Avatars are world-dependant and you must use one from that worlds avatar list.
- No physics. There is slight emulation of physics, but no actual physics. I.e. avatars can "jump", and colide with objects/otheravatars, and you can emulate physics with scripting (poorly), but thats about it.
- No real grouping method. You can use shared "privliages" (you can allow another user to have your priviliages simular to the system SL has, but slightly more) which could allow for group building/access, but its not a true grouping and one person could go rogue and screw everyone.
- Dated graphics. The graphics are still rather "low". This however has the advantage of being able to run on older systems.
- Poor company handling. Even There Inc. (Forterra) looks good compared to ActiveWorlds Inc. or whatever the hell they call themselves now days (they've been through about 5-6 name changes). Company support and general updating activity or service has been lacking for many years and is in large part why alot of the community left.
- No economy. While this is actualy good in some cases, there is no built in economy, you could however make your own using a bot, however I imagine this would be hard/difficult/annoying.
- No fullscreen mode. AW is always ran in windowed mode.
- Very limited GUI customization. I.e. both SL and There have customly graphical GUI's, however AW uses mostly default GUI Look with only a few skinnable icons (newly added).
- Non-cross platform. To my knowledge AW is highly Microsoft dependant, the built in browser uses IE (simular to There, although AW isn't as heavily reliant on IE), and also streaming video requires you to have Windows Media Player 9. Making AW look to be it will never be cross-platform.
- Limited Terraforming. Most of the time users building in a world can-not terraform the ground, only world owners can terraform. However some users have pulled this off using bots.
- Graphics "stutter" or "slow" when using the interface.
- Tourists (trial users, unpaid users) have limited access to worlds/features.
- No wind, clouds, or other enviornmental things. These can be emulated using the minor-scripting system and objects however.
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Long list, but thats all I got for now.

In large part, I like AW because of the creational freedom, scripting (what limited they have), building, etc. are more than you can do in places like There in some ways, however more limited than what SL offers.
Bots can be used to achieve alot in AW, the best worlds I've seen use a combination of bots and custom sculpted objects.