Building a trading platform with charts - suggestions for a Python GUI Library

I am building a small program to retrieve data from the market and chart it in real time. While the trading decisions will be largely automated, the charts are updated continuously so that someone can keep track of how the decisions are being taken and manually intervene when necessary.

What would be a good GUI Library for the task (for Python). Here are the considerations -

Programming Language : Python (Do you think I should use something else? May be even do the GUI and backend in different languages?!!).
Operating System : Preferably cross-platform, but if it has to be platform specific, then Linux it is.
Speed + Learning Curve : While time (low latency) is not a critical issue and I would prefer something easy to use and fast to learn, the program has to feel responsive and I would not like to trade speed for ease of coding beyond a certain point. I guess this is the part where your experience could help me out.

I had strongly considered WxPython, but some of the comments said it was not well-designed (as in, doesn't fit well with Python!)

So the complexity of the task and meta-considerations have been laid down in front of you. Please help/suggest.

P.S. : While we are at it, if someone could comment on a suitable charting library as well, it would be nice.