i love my aftermarket clifford remote start on my nissan, it has great range (about 2-3 city blocks) and it alerts me if the alarm is triggered. and if i want to jump out of the car and grab a coffee without shutting off the engine, i press the aux button 3 times and take out the key and leave the engine on and the vehicle armed. the only disadvantages of it is that it needs a spare key to be in the car at all times.
but think about it, if you had to restart the car everytime you remotely started it because you opened the door, you are taking one more start out of the life of that starter. it might be more beneficial in the long run to get an aftermarket starter even if the key fob IS nicely integrated into the key. i was also thinking about purchasing the factory remote start for my new sr5, but the open door kill switch and short range may just be the deciding factor to go with the aftermarket.