Programming language and graphics API for the generic storyline editor

I've been examining a couple of different programming languages and API's. The first is java and swing; java is the most widely used programming language, and almost always the most efficient one in terms of the number of necessary CPU cycles while maintaining stability.

It is, however, prone to several problems: Java garbage collection leads to annoying "jitter" because it isn't designed for maintaining a smooth user interface. Secondly, java swing looks weird on both windows and nix systems, being visually different from native window rendering.
Finally, java is...well, annoyingly heavy to write.

C# and windows presentation foundation is option number 2...C# is a smaller and less utilized language than Java, but it's only properly supported on microsoft platforms. Windows presentation foundation, while teoretically just what I'm looking for, is currently under-utilized as well. I don't quite dare jump on C# for these reasons...well that, and I don't like being limited to microsofts platform unless I have to be. C# is also a fairly heavy language to write.

Third option: Python and Clutter or Cairo. Clutter is a visual open source API intel is developing that can do all sorts of neat tricks. Python is google's favoured programming language, and they're currently actively developing solutions to it's biggest drawbacks. Cairo is a visual open source api that isn't being shouldered by any specific company, but it's big enough that the mozilla foundations gecko rendering engine, used in firefox, relies on it.
There are bindings from python to both api's, meaning that they should function with it; python is, itself, a language with a fairly large user base (bigger than C# and small than java), and it's dead simple to write and use. Very fast. And Clutter and Cairo look excellent; not necessarily like something that runs natively on any one system, but then, it's so fancy that it looks more next gen than simply different.

I'm hoping to use python and clutter, and if that doesn't work out, python and cairo.