i called 'em when i hadn't seen it late yesterday...
they tell me that, yes, the rollout is phased. unless your number has been called, you can check for updates all you like...ain't gonna happen. once your turn has come up, you should (but clearly may not) receive a notification. if you ignore (or never get), you can initiate the update at a later time by doing a manual check.
also, i have zero cell service at my house...not 3g, not 1x, nada. i downloaded the update last night at home, after a manual forced check...thus it must be checkable/deliverable via wifi.