I never thought Ubuntu prided itself on being a bleeding edge distribution. So, what's the problem? They've got the stable 2.6.28, and they've got... 2 months to fix whatever bugs need to be fixed. Good call on their part.
They shipped an unreleased version of Firefox in an LTS release and I think everyone that struggled with PulseAudio would disagree with that statement. However, they haven't forgotten they run servers too so I expected them to be reasonably conservative with choice of kernel. I look forward to it anyway, skipped 8.10 and will go from 8.04 to 9.04