Because Windows 7 is, of course, not completely and totally finished (as I'm led to believe) it still has a few minor errors. I myself have downloaded and run RC1 through a VM and I have to say it is bliss compared to Vista. It's smooth, everything works like a charm... it reminds me so much of XP it's not funny. And here's the kicker - a lot of the programs that fail dismally on Vista work without a hitch on W7!
This is what Vista should have been, but wasn't - don't take that the wrong way, it's not supposed to be a fix for Vista, but you can see the similarities.
It's like they took the delicious eye candy that came with Vista and took away the horrible cough lolly of the actual OS. I'm considering an installation on my 64-bit lappy running Vista right now, because... yeah, it's just so much better. I have hard some hardware/software issues, but that's to be expected - it's only a release candidate, not the finished product! A lot of the more... uhh, let's say... 'high profile' (for want of a better word) companies have almost certainly started developing drivers and upgrades for their hardware/software respectively. It's all a matter of time!
So yes, it is worth it for me, but in reality it depends on your system. If you require certain hardware/software which isn't working with 7, it might be a better idea to wait until after they release the final version and companies have started upgrading their hard and software.
Sheesh, you never get this problem with Apple. I really need to get me a MacBook I've heard through friends that the latest model works fine with dualbooting, so if that's an option, then sure!
...Wow, now I feel like such a nerd
Chris