I bought the Full Home Premium version from Newegg. It came with 32 an 64 bit versions. They are on two separate DVDs. You can change your mind later and install the other version if you like.
I think Windows 7 is great. I especially like the new task bar. I'm running the 32 bit version because I have hardware that I doesn't have 64 bit drivers. Eventually, that may change. Now that I think about, I think the 64 bit drivers I need are available.
The reason I got the retail version instead of the oem version was so that I can move it to a new computer if I want to. I probably should have gone with the oem version like I usually do.
BTW, you are really only supposed to be able to get the OEM version if you buy it at the same time you are buying hardware, like a harddrive etc.