I'd just like to shed my exprience of Windows 7, 32 and 64 bit on this post.
The 32 bit software appears fine but early on suffered from some minor security problems that were not present in the 64 bit version. These flaws were subsequently fixed and i'm sure they were present in the 64 bit version too, but they are less likely to be exploited when the code for the exploit is generally coded on a 32 bit level and the 64 bit OS just ignores it.
This is one of the reasons i used 64 bit over 32 bit, although i still run 32 bit on my netbook as it cant take 64 bit.
Next thing was when I initially tried Windows 7, I had only 2Gb RAM. I could literally run Windows, Firefox a music player and occasionally a game i was playing would crash, this is because 2Gb is just not enough for 64 bit. If you have less than 3Gb of RAM i do not recommend you use 64 bit, 4Gb+ is more optimal but 3Gb should be the MINIMUM for 64 bit consideration.
Lastly a lot of video players and editing programs for photo and video support 64 bit processing and its associated memory addressing and these often run like lightning. The same goes for compression (zip/rar files) and audio encoding (converting to mp3 etc).
It is true that you may not see a difference in games and the like.
Drivers for 64 bit can be a problem, especially if you have some devices that are not too prevalent in the market or dont have decent support.
But if your pc is relatively up to date, most if not all your devices should work. Of course, there is always the chance that your 32-bit driver wont work anyway on the 32-bit version of Windows 7. So you might have to update hardware to move to it anyway....even though in my experience Windows 7 driver support is very good out of the box.