While I have done the old install and updated, I wouldn't do it now. You have to change your sources.list and then update to update pack 3, get past the gstreamer problem, and then update to update pack 4. This will probably take at least a day. The stable isos have passed testing and will be out in the next few days, so I'd wait for them. Also, there aren't any show-stopping bugs in the rc, although I would still wait the extra few days for the stable at this point. If you don't care about them getting the official announcement (which isn't recommended), you can download the stable ones that haven't been oficialy announced from here: http://ftp.heanet.ie/pub/linuxmint.com/debian/
(download the 201204 isos).
Dell XPS 15 l502x - Debian Testing 64-bit NetInst Xfce, SolydX 64-bit Debian Testing, SolydK 64-bit SolydXK Testing
Old Gateway Pentium 4 Desktop - Arch Linux 64-bit Xfce and SolydX 32-bit Sid