Hmmm ...
I'm going to have to offer my two cents on this one, as I'm also a Therian, and none to pleased to watch my world die.
You see, both SL and There have their pros and cons, and I can be objective in analysing them both. I came to SL a few days ago and was indeed amazed at the open endedness (?) behind both code and clothing modeling. The fact that you could turn into a slavering radioactive glowing tentacular werewolf/3 year old girl hybrid is pretty cool, too.
But moving on ...

There was indeed limiting in many (many many) ways, but its simplicity was also its beauty. If you wanted to relax, you could, knowing someone wouldn't pop in on you with his latest SRGTW/3YOG hybrid avatar. They were just people like you and me. It may sound strange, but that's awfully comforting.
I'm also a wanderer. I'm the kind of guy who loves to hop on a hoverbike and ride around for hours ... and There offers me that ability. I'm not sure if you are aware of this, but There is a real planet ... its a sphere 12000 km in diameter (albeit 99% covered in water ... errr ... blue concrete). I know I could hop on hoverbike on Nata, the southernmost island, and ride northwest for an hour or more at roughly 90kph till I reached the northern island, then hop on a hoverboat and ride over the ocean for 2+ hours to reach the impressively dark island of Tyr. A whole slew of us took track of one guy who, for the fun of it, flew his hoverboat out of his funzone, due east, and didn't stop until he got back home, a three week around the world trip. During that time, I could also spend some time chatting with some geek friends in the ISS, a space PAZ 152km above sea level, in low orbit ... you could walk to the edge and look down and see the curving blue sea or drop off and fall for nearly 90 minutes before hitting the surface.
It's a very social atmosphere, and has tools specifically designed for personal interaction. Yet, has plenty of open areas if you wish to be alone or just ride a buggy with a friend, climb a high peak, and look out and see the world for miles around (without lag). In SL, virtually every plot of land is owned by someone ... pretty, creative, fascinating to the extreme ... dangerously claustrophobic.
I love the full duplex voice and chat bubble system. I don't mind the IRC style interface too much as I myself used to spend my days on IRC a few years back ... but for this, it is lacking.
I love the extremely natural movements behind the vehicles and the avatars. The fact that they're the only ones who work on the physics of a vehicle is indeed restrictive, but it also means they have all the time in the world to perfect it. And the avies in SL need work, guys, seriously. I heard avie animations will be customizable in version 1.4 and I hope someone takes the time to create a good walking and running script

There's major flaw is that they were too posessive of their creation and didn't feel they wanted too much input from their members, as far as I'm concerned. Either that or whoever took over management of the business focused much more heavily on the business side of things than on the customer end, and hence felt the backlash of people crying out for constant change and a need to take control of their world and its economy. For that, I commend SL in major ways ... you guys have a waaaaaaaaaaay better rapore with Linden than we did with There inc., although many of the staff had close friends among the membership, and even now are working hard to find a solution to preserve There's future as a virtual hangout.
Honestly, I think in the end, they likely saw a lucrative opportunity that did not demand they cater to the seesawing needs of thousands, and instead of following a path of better communication, they bailed and focused on building up the engine and everything surrounding it for licensing purposes.
I'm still testing the water in SL, so to speak, and so far, I have found many things I really like and many things I dislike, compared to There of course. Two different worlds, two different target markets, two different feels. One allows you to do anything you damn well please (thumbs up, guys), the other wishes to solely offer a few things of their own creation ... but does these things very very very well.
So yeah, I would dearly miss There ... wasn't perfect, far from it, but it was very immersive and very comforting, truly a home away from home.