A simulator can sometimes fail to help you figure out even these "general problems" though, as often times some of the conditions inside the simulator do not match those that would be present in physical hardware. For example, simulators often start out with memory zeroed out, whereas this is not typically the case in hardware. I was recently simulating code which summed the elements of an array, and I had a bug in which I included in the sum a byte one past the upper bound of the array. Because that location was otherwise unused, and initialized to zero in the simulator, my code simulated just fine, but generated incorrect results on real hardware.

In short: emulators have a real value.

--Sasha Jevtic