BPs are amazing for discovering how to use the engine - they provide a sort of guided exploration of things, especially when you don't know what you don't know.
For us they really, really, really broke down when it came to version control, multiple people working on the same BP, code reuse, and refactoring. Arguably, at least some of this was our fault - I think you're "supposed" to do the major coding not in BP and then use BP mostly for really high level stuff, and we didn't always do that.
Anyway, it's been wonderful not having those issues anymore. Gone are the days of changing one thing and then git saying that 100 files have uncommitted changes!