Not really OEM, but I'm running 11.04 on an Acer 3810T laptop. I am getting 6 hours on it with wi-fi, and the battery has lost about 10% of its charge capacity. With a brand new battery I could see it getting about 7-7.5 hours.
An OEM with a newer processor and an SSD should be able to hit 8 hours easily.
I have the 3810T too and I can report similar numbers. But still, I get more life when I boot into Windows. Moreover, suspend & hibernate just don't work & the laptop fan always stays on.
It could be a buggy BIOS for all I know but we could still do better. Thus, an OEM option where _everything works_ would definitely be nice.
I do have the v1.28 BIOS. And I think I did try that and all the other options I possibly could when I first got this laptop. I've just settled for the loud fan. Anyway, I'm going to upgrade to the new release and see what that brings!
An OEM with a newer processor and an SSD should be able to hit 8 hours easily.