No it works fine. Just note you cannot install windows 7 64bit just by inserting the dvd into the drive and running it in vista. Since you are going from 32-> 64 bit you have to do a "custom" install, so backup anything and everything that might be of value.
This is correct (+1). Put another way, you can't upgrade from a 32-bit version of Windows to a 64-bit version. You must perform a "clean" or "custom" install.
Boot from the DVD and proceed with the custom option. Pretty easy from their.