Over at reddit.com, we rewrote the site from Lisp to Python in the past week. It was pretty much done in one weekend. (Disclosure: We used my web.py library.) The others knew Lisp (they wrote their whole site in it) and they knew Python (they rewrote their whole site in it) and yet they decided liked Python better for this project. The Python version had less code that ran faster and was far easier to read and maintain.