Ironically my "wow" moment was getting 3.5G reception outside my house.

Inside I get a weak 2G signal, but even outside no other device could ever get a 3G signal before on O2s crummy network. Either O2 upgraded something recently, or the N900 is REALLY sensitive.

I did notice I lost 3G if I held the N900 on the right though (where the antenna is) which can be tricky during extensive use, as my left hand gets tired.