Android

The reception is very good on voice calls. Data transmission is excellent as well but is only EDGE speeds on AT&T. Speeds are good enough for browsing and most data needs however you will want to use wifi to download podcast and such.
I like the OS however coming from S60 (Nokia N95) Android seems less mature. Android has less apps built into the OS but I am discovering you can add many of the missing features through the Marketplace store most these apps are free. Overall the OS is very good and updates have and will come frequently.
The favorite things for me about the Nexus One is the high res AMOLED display and the Snapdragon processor which makes this phone fly. I like the customization of the 5 homescreens and the Voice to Text feature. I like how easy it is to search for and add applications.