Only because I've been there. The first company I was with - a dot com - was *exactly* like this. We never made plans for Fridays. There was one stretch when I hadn't been out on a Friday night in almost four months - needless to say when I did go out (with some others from work) it was *not* pretty. (Let's just say I couldn't work the next morning either?)
I'd spend the four days they're developing working on process improvement... I'm sure they'll be open to change
Don, I am SO sorry to hear that!! Believe me, it was a good six months before I saw a Friday turn out right... And I would get SO angry every time I tried to make plans.
Have you considered leaving early those days, or coming in very late, if you know you're going to be there late? After about a month of the "late builds", we started coming in at noon on Fridays, or leaving at noon and coming back at 4 for the builds LOL.. That way we at least had SOME time to ourselves. It's not perfect, but it was a bit of a help...
In my former job it was the wednesday that i hated. Next to testing i was responsible for the customer support and all the customers seems to call in or have troubles on wednesday. The friday was not so bad because we all agreed not to deliver any new software on friday.