Yes, we are providing and supporting updated NVIDIA drivers in Ubuntu.
Update your system, then look in Additional Hardware Drivers to see the available update options. (Scroll down if necessary.)
nvidia-current (version current) is what was stable at the time of the ubuntu release. This is your baseline driver. We never update this driver (except for critical packaging fixes) post-release.
nvidia-current-updates (post-release updates) is a newer version which our testing has found to be reasonably stable. We can't guarantee that, which is why we provide it via this opt-in package. We update this driver periodically, usually within a few weeks of an update becoming available.
nvidia-experimental-304 should be ignored. We may provide some updates here but these won't be that interesting.
nvidia-experimental-310 (experimental beta) is a very new, unstable, bleeding-edge version that we have done no testing on. But it will give you the latest and greatest NVIDIA support, and if you want to run Valve Steam games at maximum performance this is what you want. Once you install this package, as new versions are released by NVIDIA we'll include them here, so when you do routine system updates it'll pull in updates for you. In theory each update of this package should become more and more stable. We are hoping to update this package in precise within a week or so of a new update becoming available.
The above options are what I'd call officially supported versions. We'll accept bug reports about them and work with NVIDIA towards finding fixes (time permitting...)
There are also PPA options via x-updates and xorg-edgers. x-updates is semi-official in that we try to keep it to known-stable versions and we accept bug reports (at low priority for fixing). xorg-edgers really should be used only by people who know what they're doing - it's really just for testers, not users. We don't accept bug reports for xorg-edgers.
For directions and more information on installing drivers for Valve Steam see http://wiki.ubuntu.com/Valve