I used to code for a website handling about 25,000 logged in users per day, and there was a post-commit hook on SVN which pushed changes live, immediately. Working on that taught me a lot (mostly how not* to do things), one thing I learnt is that I code much, much faster under that kind of pressure.

* Note: I am not endorsing this as a setup, it's crazy. I don't think I've ever seen such high staff turnover.