OK, after the PDC this week and looking at all the news about Win7, it's my opinion that you are going to be fine skipping Vista and upgrade to Win7 when it comes out, or even after Win7 SP1 has been released.
There has been a LOT of information released this week, since the pre-beta is now available and the main features have surfaced. Some people claim though that Win7 really is putting lipstick on a pig, and they say performance at the moment seems to be the same as Vista, and it's just as consumer focused (and sometimes confusing) as Vista.
Others claim that Win7 is tighter and leaner, has better device integration and has a bunch of IT-friendly features. A change like the elimination of in-memory double buffering of window contents, will make a huge difference in the memory footprint and overall demand.
I think that Redmond has learned some lessons and that the wait for Win7 will be worth it.
Expect general availability in Q1 2010 if the operating system remains on schedule.