As on OS X user I have used a slew of text editors (SubEathaEdit and TextMate being my favorites), as well as Eclipse and a handful of others ... in the end I have settled (at least for the moment) on Panic's Coda.

Very nice total site management tool with PHP code completion and built in reference books for PHP, CSS, JavaScript and HTML ... not to mention multi-user document editing (via Bonjour), FTP, live previewing and shell command access.

Best of all the interface is uncluttered and easy to use.