This has been discussed a bit lately, and I thought I would throw in my two cents. Why would you want to run 64-bit versus 32-bit on your personal computer? Simple, your 32-bit operating system contains a ticking time bomb (no pun intended) that could likely explode causing problems for you creating headaches.
It is known as the Y2K38 bug, and it comes to life Tuesday January 19 2038 at 03:14:07. If you're not running 64-bit, your computer, or embedded system, will likely show the next date following as Friday December 13 1901 at 20:45:52. This is due to 32-bit systems running that are using the UNIX epoch timestamp. Is this a problem? Most definitely! You probably will not notice it on your laptop or desktop for casual use now, and you probably won't notice it in 31 years, as we will most likely be past 32-bit, and possibly even 64-bit when it comes to our personal machines. After all, look at the past 30 years and how far we've come. However, look at embedded systems, such as microwaves, tvs, routers and thin clients. Many are 16-bit and even 8-bit systems, not to mention 32-bit. Look at code. I have heard of 8-bit binaries in production that were written 20 years ago still in production. Will 32-bit code still be in production 31 years from now? Very likely.
So, to add to the arguments of whether to run 64-bit or run 32-bit, I suggest running 64-bit just in case you write software that may be in production in 2038. I also suggest running 64-bit to prevent existing software from having issues in projecting future dates past January 19 2038. So there you have it. Run 64-bit.