One of the largest problems for 64 Bit users is that there is no official 64 Bit version of Flash, by Macromedia. There has been an online petition started to get Macromedia to develop this. Although it may not currently affect you if you are using a 32 bit operating system, you should still sign this petition because it may affect you soon (more than likely the next computer you buy will be 64 bit)

Here is the Petition (I am signature 5156)