Did you consider Pyramid? It's insanely flexible, has amazing documentation, doesn't make any assumptions about the kind of applications you want to build with it and has a "pay only for what you need" philosophy. I'm currently using Django for my projects because it's a good fit for them (CRUD apps that generate static pages; zero frontend wizardry), but if I were to write a frontend-heavy webapp that talked to a server using a JSON API, Pyramid would be my first choice.