There is one concern for watching anime on Win7 with MPC, you may have an issue with subtitles not showing up at first. I believe you have to add a filter for DirectVobSub (under external filters in options). I can't remember the details and i can't seem to find the old thread that talked about this issue. It's not that big of a deal though, and i fixed it in 5 seconds.
The new CCCP, 09-09-09, fixes that problem.
I did a full clean install of CCCP (and i had already had 09-09-09 before on Vista) but it still woulden't show subs until i added the filter. /shrug
And as far as Vista was concerned i thought it was fine too but after the first few months i started getting chipset driver corruption errors and i couldn't run anything that was too graphic intensive. Consider that my laptop runs a GeForce 9600M GT with a C2D T9400 @2.53 GHz and i was having problems running 720p videos and games running at 5-15 frames; i was pretty annoyed.
After i upgraded to Vista SP2 It fixed my chipset driver issues but i was getting random spikes in my CPU at odd and completely random times, where it would stick at 50% or even 100% utilization and stay that way until i restarted a couple of times. Much of the "Vista is evil" i admit is negative hype centered around the huge missing driver fiasco at release along with the OS being a memory hog in general (RAM and HDD) but some of the criticism was well warranted with random shit like that that's happened to a few people.
Sorry. I don't want to make this thread about Vista, just had to put that out there.