I've been using Netbeans as my IDE of choice for quite some time, it is cross-platform and has support for every language that I use with good tools.
Unfortunately, netbeans is stopping support for python with version 7. (python support has been a community plugin anyway) So I'm forced to find something new.
I'm trying out wingware's python specific IDE and I like it a lot, the license is quite fair and it seems to have everything I need for python at least. I thought I'd post and see what others use as well though.
For a long time I've used SciTE on Windows, though to be relevant to the topic it's not really an IDE, but rather something like an even more stripped down Textmate. More recently though I'm using Emacs. If you don't mind its quirks it's really great. Vim is also an option, but in my opinion its lack of support for asynchronous operations doesn't lend itself to dynamic languages like Python. The other Python IDEs seem somewhat interchangeable to me, and not really worth investing much time in.
edit: if you really want to shake things up, try out Leo + the iPython bridge.
pysmell I'd never even heard of. Thanks. I know a lot of people look for the minimalist approach and like it. vim is a bit too far in that direction for me. It seems I can find very little that has everything I want, in the way I want it, without using a commercial product. Komodo has it, but too expensive. Pycharm looks nice, but I think it needs a bit more maturity.
I think I'm going with Wing. It'll be the first piece of commercial software on my personal use machine. For me, I will generally swing wide around commercial products for my own use because of the restrictions in their licensing, but this one actually seems fair.
Geany was being flaky in a couple of features but after I rebooted it seemed to work ok. I sometimes forget windows is that way. A little lighter than I want, but it is oh so close.
I guess I look for a "middle-weight" sort of beast. An editor with completion isn't enough for me and something like Leo is way too much.
Eclipse + PyDev is what I've been working with the most. Excellent integration with my unit pylint/unit testing/coverage.py setup, and it catches a lot of code/formatting errors before I even commit. It is a bit ugly to configure, and very slow to start up. There are also a ton of features I don't ever use.
vim if I'm editing remotely or proofing something out really quickly.
I've used Eclipse with pydev for a college class, and it seemed to work pretty well. The downside is that if you code in Java too you have to switch back and forth. I don't like IDLE, especially as it doesn't even function as a proper text editor. Although I suppose one could use an editor (Notepad++ anyone?) and then use the command line or something to run it/compile it to .pyc. I tried Netbeans once or twice, but Eclipse seems a little easier and in terms of load time very similar.