Oneiric Beta 2 comes out with improvements in multiarch support, kernel 3.0.4, an update to Gnome 3.1.92, and lots and lots of bug fixes (of course).
Multiarch support lets you install 32-bit versions of supported software on 64-bit Ubuntu sans ia32-libs. We're getting ever closer to not requiring ia32-libs anymore on 64-bit Ubuntu setups.
Kernel 3.0.4 is the latest stable release. Unfortunately, it doesn't have a fix for the power regressions we're having.
We're expecting Gnome 3.2 for Oneiric, so an update to Gnome 3.1.92 is just keeping things in sync with upstream. Hopefully Gnome Shell support will see some improvements but seeing as how Ubuntu doesn't officially support it, it's going to be hit or miss.
As always, check the list of known issues available in the Technical Overview before any upgrades to minimise the pain.