That Ubergizmo review makes for interesting reading. The battery test is especially interesting and if accurate, makes it look like MS were fairly conservative with their estimates of 4.5hrs.
If it can last a solid 6hrs of productivity (Office, web, etc) that's more than enough to last me through my work day as it will be asleep for some of my 8hr day.
Fortunately it looks like the better reviews are actually coming to the front more quickly than they did for the RT though the "mass media" sources still aren't doing a very good job for the most part.
I noticed in Engadgets battery test the RT got 9 hours and 36 minutes, and the Surface Pro managed 3 hours and 46 minutes. It is a stress test of sorts.
I think some of the better reviews I've read tend to be from people with a bit more experience with the RT, maybe with a little more understanding of the benefits of the form factor from that experience.