At this very moment FPSC X10 is lacking support because the majority of users are still on X9, most people don't feel like switching to the memory hog called Vista just for some shiny graphics while X9 still has the most features mod-wise, and most models available.
Look at it this way, if they update X9 the X10 users will whine, If they update X10 the X9 users will whine... There's always one unhappy party and there is no way to change that, we just have to accept that TGC is limited programmer-wise. I'm sure they'll get to patching up X10 as soon as they're done with most issues in X9, or when the majority moves over to Direct X10.
In my personal opinion it's worth buying and yet not. You should really figure it out for yourself. If you dislike the lack of updates and support right now though, I suggest you wait a little, and see if the price drops later on when they do release updates and such. Since you might not use it at this very moment anyway.
It's not the world that turns against you, it's you that turns against the world.
