The N900 loses signal in areas none of these phones do with Tmo where I live:

N-Gage
Sammy T349
Nokia 3610
Tmo Dash
SE Walkman phone
G1

All six of these devices work in areas that the N900 does not. Easily the weakest GSM signal on a phone I have used. Works great in medium to high signal areas and phone call quality is super clear.

Still love my N900, but the signal thing is killing me

My G1 is far better with signal in weak areas than the N900. No contest. G1 is weak as a device compared to the N900, so the irony is tough.