The ease of use! It's so easy to set up that it can be done in less than 5 minutes (and this includes installing all required components). I have not found any problems with wampserver yet - everything works as expected out-of-the box without me having hade to do anything special or hack into things like other servers require you too. If your server crashes then there are plenty more services available from different vendors which will help fix issues such as memory leaks etc., but if yours does crash once installed using wampserservers service pack 1 fixes most common crashing errors encountered during startup/shutdown processes.