I work on a sizeable desktop application written in PyQt. While I agree that Qt has a very nineties feel about it, you don't have to buy into that. Specifically, you don't have to use class hierarchies to model your domain. It actually helps to have a language boundary -- we can let Qt be its object-oriented self, but on the Python side it's different. We do a limited amount of subclassing, which lets us hook into user interaction events, but other than that we use whatever works best in Python. As time passes, this seems to involve more and more straight-forward procedural code, less and less object-oriented modeling.