Today (2/8/2009) around 5pm EST, my G1 displayed this message:

A system update is available
While your phone is updating, you cannot make emergency calls. Your phone will restart during update.

It updated and rebooted twice. Anyone else get this as well?

It updated to RC33 and Firmware 1.1. Google voice search app is now installed and there is a 'Check for Updates' option in settings.

I just found this link to T-Mobile'site forumes which has more details:
http://forums.t-mobile.com/tmbl/board/m ... d.id=30897