I use a NAVMAN R300 for a week now and it is awesome! You don't need to mess with PCs, you just strap it on and hit the road. It will automatically tell you all you need to know: current speed, pace, average speed, max speed, distance run at any time, altitude (actually it can be useful if you are preparing for a hilly marathon), calories burned (it overestimates this one). If you are patient enough you can easily figure out how to set speed/pace limits for your sessions and the NAVMAN will beep every time you violate them -or- you can set lap times (if you are running on a track). It is very accurate and the GPS reception is flawless, I use it around Athens (which is a rather densely built city) and it works fine. You can also use it as a pedometer. Hope this helps!