Agony...pain...frustration. The deathmarch to a release is the worst part of software engineering. The second worst part is the boredom that comes in the days immediately after, when you can't check new code in because the release hasn't been finished yet. But at least its a relaxing kind of boredom. And you can go do all the things you hadn't done in the weeks prior, like pay your bills, shave, and go mountain biking.
Well, it certainly is nice to have contributed major pieces to a release at last. Previously, my checkins had barely been a footnote to the development activity.