I finally found Komodo Edit which is the open source, slimmed down version of the Komodo IDE by ActiveState. I immediately liked it very much! It's not ultra fast and slim like a text editor but it's not even a hog for my machine. The only thing I really missed was a feature to see the list of functions in your code (which is included - of course - in the commercial version). Luckily there's a free plug-in called Source Tree which implements nicely this functionality.
Everything is free and runs smoothly. I haven't honestly tested for long but for my quick hacks is definitely a great thing.
Give a look to Komodo Edit at the Open Komodo site.