Now functional programming languages are scary to any student who sees them for the first time, but I admit, this kind of thing really scared me. Took a CS Introduction to Functional Programming course at university, taught using Clean, a pure and lazy functional language developed at the university. Most of their research currently is related to iTasks (see http://wiki.clean.cs.ru.nl/ITasks) which also does web apps, but focused on workflows. As a web dev however, it totally stripped the layers between model and browser, which is actually the harder part most of the time where the customization happens, and became this (all too simple) mess of models and functions. It was too early stage software too, various server bugs in the built-in HTTP server, and lacking JS/frontend implemantation. Only one of the 15 weeks needed iTasks, which was a good thing, for students and TA sanity.

Interesting story, though it's tough to gather what your overall point is. You're saying that abstracting server and client logic into monolithic functional code gave you headaches?

Sorry, it was late. I think my point was that you can't reduce the "science" of a web app to pure functions...