Travis,
I'n no engineer, so take this with a grain of salt. I'm curious as to what you are working on this year that is so critical with respect to bearing eccentricity and the actual difference between a reasonably high-precision ball bearing and a decent bronze bearing. [Especially considering last year's effort without bearings

] Bronze bearings aren't all that bad, mostly depending on lubrication, of course. As far as friction goes, sealed ball bearings do need to come up to operating temperature, don't they? Do they achieve this in a match?
I would think losses in other stages of the drivetrain/chassis would be more significant than this (alignment, gear losses...). I can see being worried about the bearing stiffness on a 300 MW generator (like this:
http://bpb-co.com/bpb/articles/2Q01bently4.htm), but not on a robot that operates all over the spectrum for 2 minutes or so. At any rate, I'd appreciate any practical info with respect to bearing applications and the like.