I generally use Nusphere PHPEd for all of my php coding needs. However I keep giving Aptana Studio a spin and then end up returning back to PHPEd. Aptana has many nice features not found in PHPEd such as highlighting the opening and closing of an html tag which is useful for when you are trying to figure out which piece of code to edit. Also you are able to attach a hot key to an svn commit. This makes committing files while writing code a very non-distracting process.
In spite of these features and the many more nice features, I am deterred from using it because of the problems that occur. For one it has a problem with losing my information. A couple of times I have opened up the program only to find that all my ftp and project information was missing. Just recently when using the program, my hot keys stopped working. This only happened in Aptana Studio. Another issue was the color coding was out of wack a few times. When I opened the file, the code was all black. I shut the program down and started it up again and all was working fine. Then the last thing that happened: I used to link my project to external libraries and was able to get documentation on a class included in the external library. That quit working for no apparent reason.
The trade off for me is really between having a boat load of useful features (Aptana Studio) versus reliability (Nusphere PHPEd).

