Well, I've been working on my new team for 4 weeks now. I've learned a lot about their process. I'm getting better at running tests and figuring out failures. I'm getting more familiar with the source base. I've learned little bits about optimizations (mostly the language used to describe them, and the underlying assumptions). Hopefully now that focus is starting to shift (less bug fixing, more planning for next version) I'll get a chance to learn more...
Anyway I'm just glad that the week is over and I've managed to clean up after myself enough to actually fix a few real bugs and hopefully not introduce anymore big regressions. Being a compiler writer, I'll never be able to say, “Look at what I made, Mom!” but at least I have lots of internal victories.