I have used PyCharm daily since its early versions and have been mostly happy with it. When I think about it, it's actually the first IDE for any language I've kept using for longer than a couple of weeks. The best features for me include code navigation, run/test/debug, refactoring, inspections, keyboard-friendliness. It's also got a decent editor and built-in support for Sass and CoffeeScript. Btw, they also provide a free licence for open source development.