i use zend studio for eclipse with the built in debugger. Its still slow compared to debugging with eclipse pdt with xdebug. Hopefully they will fix those issues, the speed has improved over the recent releases but still stepping over things takes 2-3 seconds. The zend firefox toolbar really makes things easy (debug next page, current page, etc). Also it provides a profiler that will benchmark your code and provide pie-charts, execution time, etc.