The main advantage as stated above is you break the 4 gig of addressable memory space barrier, that is about it. So, if you feel you need more than 4 gig of memory, you need a 64 bit OS. If what you do works fine with 4 gig or less, there is no reason to move to 64 bit.
There is no problem with 64 bit OS drivers or other issues with modern programs and hardware. Most issues are the fact that some programs simply won't work under the Vista or Win7 kernel, which is what you will be doing if you move to a 64 bit OS. If the program has issues with Vista or Win 7 64 bit, is is likely going to have the same issues with the 32 bit version. You can solve that by getting the Ultimate Version, which has XP compatibility mode. 64 bit drivers, you only need to worry about old hardware, like if you have a 10 year old scanner or printer, you might have an issue. But Microsoft has a program you download and run to let you know of any issues with your system before you make the change.