#1 - There was a bug a while ago that let you make vehicles with more prims. It worked great, though if it was in widespread use it might have been a load on the servers. Basically physical stuff lags the crap out of this game and so LL needs to cut down on it as much as possible.
#2 - Well I dont much about how the sim-to-sim thing works, but distributed systems suck

Well they dont suck, its just that we coders suck at grasping them because so much stuff is happening all at once and in so many different computers. They're usually seen as hard to debug because of that, but I really dont know at all what the problem might be with the sim lines

#3 - You can easily do flight plans with scripting already. It wouldnt be hard for people to make a flying train of sorts that stopped at stations around the world, and waited a certain time for people to board it before proceeding.
#4 - It may be because 256 is a sort of magical number for coders, since its the maximum number you can usually put into a single byte. This is probably never going to be changed, as sim coordinates are actually part of a global system, and it would probably break a lot of stuff if we had sims of different sizes, or a bigger size for every sim.
About what Ama said, I think right now a sim can only be adjacent to one sim per side or something. There was a post about this somewhere a few months ago but I forgot half of it.
#5 - The land texture is actually a bunch of different ones put on top of each other. You can get their keys from some file in the SL folder and pass them to llSetTexture. This is how people who live in holes do those cool, ground-looking covers.
#6 - The primitive shapes arent determined by the lindens. They are the standard geometrical primitives in OpenGL and Havok, and I think that because of the way they have coded the system, they cant add more prims unless there are some changes made to Havok and OpenGL. You see, in order to get all this fancy 3D world streamed to you fast enough to be playable, they had to come up with a clever scheme, in that the only information that is transmitted is the type of primitive and its geometrical characteristics, like size, hollow, etc.
So they can only use the ones that come with the programming software they use, Havok for the physics calculations and OpenGL for the graphics.
#7 - Sounds like a good thing to have! Uh, it doesnt do this already? It really sounds like the most logical way for it to work.
#8 - When they're done. Bug Xenon, I think he's the guy in charge of the meshes.
#9 - Didn't they say they fixed object ghosting? It's odd but it still happens. Well, I'm not gonna go into fancy consistency algorithms, but let me just say that keeping data consistent and coherent across several programs or machines is something that computer scientists have given a lot of thought to. I'm sure LL will get it right eventually, as it is one of those things that not just any programmer will be able to get 100% right in one try. See #2

#10 - Never. Sorry, beta aint coming back, shadow. Every plot of land that LL keeps empty is money they are losing. If you want to see LL remain financially solvent forever it isnt in our best interest to have lots of land go unused and unpaid for.