Downloaded and attempted to install 64-bit Beta 1 today-- got 3/4 of the way through setup, it told me that Windows could not be installed on this hardware, exited. No details given on what was incompatible. Had to restore XP from a Ghost backup. CPU is Athlon X2 5050e, motherboard is Biostar MCP6P M2+, video card is Galaxy KFA2 Geforce Nvida 7300LE 256MB.
Edited to add:
By 3/4 through setup, I mean that the installation started, it worked through to the bottom item on the list of installation tasks, and the installation progress bar on the bottom of the screen had reached around 3/4 of the way across the bottom of the screen-- maybe half an hour into the installation. After that point was where it said that it could not be set up on that hardware. Reboot, it shows a screen that "Windows is starting services" or something like that (may be a standard Vista message, I've never touched Vista before) and then gave a message that setup wasn't complete, and I needed to re-run setup. Rather than attempt the install again (and surely see the same error message) I Ghosted XP back on.