Of all mobile software platforms, I have extensive development experience with three: Windows Mobile, BlackBerry and iPhone. For all three, there's a simulator for ease of debugging. And here's my expert opinion: the Microsoft Device Emulator is the best. The BB simulator does not support multiple debugging sessions in a row - if you change and recompile, you have to restart the simulator, and that takes a nontrivial amount of time. The iPhone simulator is not that bad, but it has considerable differences with the real device. Also, you cannot run arbitrary software on it - the simulator does not actually simulate the ARM CPU of a real iPhone, it runs compiled Intel code.
Microsoft Device Emulator, on the other hand, emulates ARM instruction set to a tee, supports debugger reconnection, and on top of that, approximates real device performance reasonably well. Hats off to MSFT. Apple Computer and RIM - you officially suck.