Parallels and Bootcamp
I haven't tried Fusion yet, but I can say that the latest available full release of Parallels (build 3188 released March 07) has superb support for running your bootcamp partition as a VM.
I use it on a daily basis (on my MBP Core 2 Duo) for running MS Visio and Project and happily switch between Bootcamp native and Parallels. The only issue I've seen is that sometimes windows needs two attempts to start under bootcamp. As far as I'm concerned, the ability to choose to run my XP SP2 image or natively or vm'd is a killer differentiator.
It's going to be interesting to see what Fusion brings to the table because Parallels already has USB 2.0, Vista, drag'n'drop dynamic desktop resizing, full screen mode, coherence (i.e. mac window mode), copy-paste, drag'n'drop, shared foldering, etc. Parallels also happily imports VMWare Virtual Machines so for individual usage I don't see see a motivator to change. If I was regularly moving VM's to non-parallels platforms that might matter but I don't.
[Disclaimer: I am in no way paid by or related to Parallels]