What Rizla said I guess... if you're a hard-core gamer and have the graphics hardware to cope, it's a significant improvement on DX9.
It all comes down to the individual's choice. If you think it's worth it - then yes. If you don't, then no. That's my outlook on a lot of IT-related options - the majority of "must-haves" for some are options for most people - and Vista for me is still in an incredibly infantile stage - not the OS itself which has improved a whole lot, but I'm referring to the reasons for having Vista - there still aren't that many at the moment, and there are still plenty of reasons not to install it. The IT world has been very slow at making the transition to Vista, both hardware/software manufacturers and users. It's getting there, slowly.
I know I was happily using XP happily well before it was 2 years old (I originally had a dual-boot with Win98 for some old Windows/DOS games that didn't work in XP), but I haven't had that for about 5 years now. Certainly at the moment I have no plans to install Vista, as the one good reason to install it (gaming) is something I don't do enough to warrant spending silly money on a graphics card to make it all worthwhile, so for me there would be little to no point!
So I suppose what I'm saying is, it isn't really possible to give an opinion whether Vista is worth moving to, as it would be simply that - my own opinion. Hardcore gamers have always been the people to get the latest and greatest - often just for bragging rights(!), but occasionally because something really is much better than previously, so they can play games at silly resolutions and Extra-super-high Detail level with cherries on top!!! It's their hobby after all, and people tend to not mind spending a bit of money to enhance the enjoyment of a hobby.
Other people upgrade computers once there really is a beneficial upgrade, rather than just for the sake of having it. Everyone has their own requirements and as such it isn't possible to generalise.
For me, it wouldn't be worth buying Vista for DX10 as I wouldn't see the benefit at the moment. For other people, it's seen as an enormous improvement and is therefore a must-have! For anyone, and this applies to any new version of a product, it's only going to be worth buying Vista when your current operating system no longer provides the services that you require from your PC, i.e. when Vista would be an upgrade rather than a replacement.
