I'm afraid I have to veto this. It's way too premature to land this in precise.
On the proprietary graphics drivers, VT switching is inherently unstable and causes lots of flickering due to them not doing KMS. Also, starting multiple user sessions at once (which is what this comes down to) has never really worked reliably on NVidia, and it's just plain broken on many (most?) machines. So far people have learned to not do user switching, but log out and back in. This forces the bug upon every NVidia user now, so as soon as the screen saver kicks in, you probably just have to reboot, losing all your session state.
On systems with multiple monitors (all drivers) the current packages do not maintain the XRandR configuration from the user session, but switch back to the X.org defaults. This causes a lot of flickering, destroys the monitor configuration (wrong resolution, re-enabling monitors you previously disabled, etc.), and thus looks quite hideous and also is very slow. Most monitors I've seen take a few seconds to get back to their senses after an xrandr switch, and our Samsung 24" takes about 20 seconds.
Please revert this. I'm afraid it still needs a lot of groundwork on both drivers and the XRandR handling before we can land this :-(