We're another that have gone with Canon for managed printers, LBP5970s are the main ones throughout the school IT rooms, MFP's are used in "areas" elsewhere. Pretty good printers overall, and like AT says, no driver issues what so ever. We're using Uniflow print management software to manage them which, while expensive is very very good and does everything we've asked of it.
I on the other hand do have some Oki experience, and to say it's not a good one would be an understatement. We have 3 in total, one was bought for the art department because it could do really long banners, it doesn't always notify our management company to send us out toners like the canons do, but when it does they sometimes can't even get stock! (apparently what happened in japan has affected these) and that's not to mention the one we've ditched completely because it was so problematic so regularly we just gave up on it. Plus our management company just tell us to bin the empties because they can't be reloaded, whereas with the canons we either send or someone picks up the empties and they get refilled which is much more environmentally friendly.
The okis also seem to make a right mess when changing the toners.
EDIT: just to add, we had kyocera before the Canons, they broke down a lot but apart from that were pretty good, didn't like the drivers much though. (physically they were very easy to take a part and get right into the bowls of the thing)
From a networking point of view, canons have been the best. From a quality stand point then it's Oki (but at a cost), being a school i know which i prefer.