VL seems to be on a pretty strong track for 64bit. Flash is working wonderfully, I've had success with both ATI and Nvidia propriatory drivers, Minecraft runs nicely too
Virtualbox runs great on VL 64bit.
Just like with Slackware64, you can install 32bit applications directly into the system if you need to.
The big downside to VL64 right now is that many applications are "behind" 32bit, in that they have not been yet updated to the latest versions. All are fairly recent, but not caught up with VL7.0 32bit Gold.
Like M0E, I run VL64bit beta1 as my primary desktop OS, and use it for development as well. I have a 32bit VL that I chroot to to cross-compile packages. I don't chroot to it for anything else.