I used Eclispe/Aptana/PyDev at a previous job and it was pretty nice, but PyCharm is superior in my opinion. In addition to great completion and code navigation, it also gets Vim emulation mostly right. PyCharm is also a mostly out-of-the-box experience, whereas it took a while for me to get Eclipse set up just right.

Admittedly I haven't tried every editor, but it seems nicer than most.