Hi. I had a smooth experience with Lucid/i386 when I ran the beta 1 cd, installing the proprietary nvidia drivers went smoothly.
However, when I downloaded and installed the amd64 version of Beta 2, I was unable to install the proprietary drivers. Both times I kept getting an error that it was unable to complete the installation, and to check /var/log/jockey.log
When I would restart, I would be thrown into console mode -but running startx or gdm manually would work.
Checking the logs, it appeared that the nvidia kernel module wasn't loading.
This is a complete hack, but it got my system working. I googled to find out if other people had this problem. I read that either the nouveau and/or the vga16fb modules interfered with the nvidia module loading.
I ran the System->hardware drivers wizard again and it failed again. Then I added the following to my /etc/modprobe.d/blacklist.conf
And now the nvidia driver shows up as being installed, and X works just fine.
I'm not sure what the right thing to do was, but for now, this works (for me).