I too have actually seen this happen. All over the place from GPRS to EDGE to 3G then back to GPRS. I haven't seen it get fixed yet from my reboot. I also noticed it gets a little worse reception then I did one my G1.
Retired- T-Mobile G2 Perma-rooted, SIM Unlocked, S-Off, Stock Rom w/o bloatware
Retired- HTC Espresso/MyTouch Slide rooted, Personal ROM
Retired- HTC Desire/Eris-Rooted...EvilEris 3.0
Retired- T-Mobile G1, rooted NexusSuperD-blk 1.9.3 Danger SPL
Retired- HTC 6700 WM6.1 Heavily Modded
Retired- HTC 6800 WM6.1 Heavily modded