Engadget has put together a side-by-side comparison of Vista vs. Leopard. It shouldn't be surprising to anyone that Engadget thinks Apple is better (the same as it shouldn't be a surprise that, I'd probably dispute that, if I had a copy of Leopard to try out), but it was a lot closer than I expected.
Vista beat out the Mac in media features (well, duh), but iLife still edges out the integrated Vista counterparts. Hopefully the Windows Live takeover of most of those apps will lead to greater improvements over a shorter timeframe.
If I were on the Windows team, I would be actively engaging with these people to find out what they can do to beat out Apple in the usability department (at least something a little more intelligent then "cuz Apple rulezors", anyways)