I've used clojure for some weekend hacking and have found that the biggest challenge is feeling like my code is non-optimal. I can get stuff to work and could build real stuff in clojure, but I hesitate because I feel that it's not necessarily idiomatic.
I guess I need a clojure mentor for the first non-trivial project. There really isn't that much idiomatic web-related code out there to read, and with clojure there is also quite a lot of variation in how systems get designed (b/c of the power and expressiveness available).
This is not an excuse, just noting the factor that has turned out to slow me down. If i had more leisure time I'd just power through and build stuff until I arrived (through trial and error) at my own sense of best-practices / design tradeoffs. That has yet to happen but will someday.