I have been through every beta blocker made and had every side effect (or so it feels...). From gaining 30 pounds in a month to super tiredness to cardiomyopathy. (All side effects were quick to show up--within days I saw the effects beginning.)
Needless to say, I don't take them anymore haha...
I take Cardizem only as needed (a calcium channel blocker) and it works so-so... but it's the last option for drugs, and I'm trying to avoid another surgery. (Until the maze procedure is perfected.)
From the other posters', it looks like I'm in the minority, and your chances are good that you'll be okay :D
Good luck, and follow doctor's orders. Don't be afraid to tell him if you don't like the side effects, though... there are lots more options out there.
--Kristin