I've installed both X64 and X86 they both installed with no problems (my comp is a stock HP
A1250N) I never had A BSOD or anything. The problem I have is speedfan and sound dont work on X64. Other than that I am using Vista for everything now XP seems so blah compared to Vista. I run the X86 now so I can get sound and Blizzard games dont work with Vista (32 or 64 bit). IE 7 takes 3 minute s to load my home page (google.ca) and 10+ mins to load anandtech.com but Firefox works perfectly.
My Experience so far:
1) Speedfan only works on the 32 bit version
2) Blizzard games will only work if you never go online and dont patch them
3) Use Firefox becuase IE 7 may look nice but its slower than dial up even if you have broadband
4) Use the 32 Bit version because of better drivers. (My system rating went from 2 to 4 by installing ATI Drivers)
This is just my opinion and YMMV but I love Vista, My 2 cents.