I've been playing with a hierarchy view recently, and got some interesting results already... In python an interesting aspect is that you have multiple inheritance, so given some class you can have a Tree of superclasses as well as a Tree of subclasses.
So, instead of using a Tree View as JDT does, I decided to try something such as showing it similar to a class diagram. After a long search in the net for 2d drawing toolkits, I've decided for Piccolo. It's a nice library, and I've had only few problems using it. A point that favored it a lot over other choices is that it supports SWT natively, without the need for any other library, and besides, its abstractions are pretty easy to follow.
The results I got so far are in the image below...
Note that the graphic part is actually the 'easy' part... doing a search for references (to get the subclasses) is the difficult thing, but it seems to be shaping up nicely. I hope to release it (at least in a beta state) for the next release of pydev extensions.