Fewer and fewer. As soon as an issue gets by our testing, we get the person who shipped the bug, and a few of our testing gurus together to figure out how to add a test for it. We've built some really impressive testing infrastructure, which we're working to open source. If I was forced to put a number on it, we may see a small issue every other day, and a larger one roughly once a week.

As soon as we rolled out the Deployment Manager we saw problems staying on production for shorter and shorter times. We see the DM as more issue mitigation than testing. The self test production framework we're continuing to build out has been hugely helpful.

The blog post is mostly about backend code. At the moment we're using selenium in more of a monitoring role (think keynote but free). We need to get selenium up and running as part of frontend automated testing, but right now we're pretty reliant on Test::Unit and some basic integration tests.