To play devil's advocate here, I have recently installed the pre-RC1 of Windows Vista and even though it IS very Mac-ish, it's quite promising. The Beta 2 was abysmal in performance and usability (I had this running on my Athlon XP that's described in my sig). Since I've installed pre-RC1, I'm very impressed with the improvements to it, and it's surprisingly fast compared to Beta 2. It felt like running an XP install on that Athlon, so that's promising.
Still, you won't get the experience you expect (even if you expect it to run slow) with Vista under emulation. It's just too demanding on emulated systems like that. However, through Boot Camp it would perform extremely well.