Mrs. Big Dog and I don't dine out much, and when we do, we don't tend to frequent "finer" dining establishments. Our "fine dining out" is Olive Garden or similar, usually.
As for pet peeves, pretty much all that has been mentioned here. I can't think of anything else. My biggest are the closeness of courses, or on the other hand the length of time waiting between courses, and waiting for refills. There have been a few times I have actually gone myself to the server station to fill my water. I understand servers are busy, but if they can't stand the heat, get out of the dining room. Having been a server myself at a family restaurant, perhaps I critique a bit more heavily then others. I recall the best tip I got came after I decided to dump the pitcher of ice water (by accident of course) on one of the guests. Prior to apologizing (and providing napkins/towels), I said that the bath was on the house. I figured I blew the tip, and just assumed I wasn't getting one. Percentagewise, it was the largest tip I got.
Of course, the grand daddy of them all is improperly cooked food. I've been lucky and not really had this problem, but I recall the one time I did, the server impressed me. I ordered a NY Strip medium to medium well, and it came out well crusted but once I cut in to it, it was moo-ing at me. I didn't even have to point it out to the server, that's how bad it was. The server asked if I wanted to talk to a manager, and I said yes. She cleared my plate, brought it to the kitchen, and hollered out "Who the h*ll is responsible for this? I kinda laughed until the manager came and offered to take a buck or two off the bill. I ate the veggie and pilaf of a $12 some dollar plate, and it still cost me $10 bucks?!?!? While swearing I'd never eat there again, I said whatever. I then went to pay for the bill and the server rang me out. She asked what the manager said and I told her. She was appalled, and took another $5 or off. I got a total of $8 off the bill, which joined the server's tip for the efforts.
Another thing that drives me insane is multiple servers. I understand for large parties, but for a small party? TGI Friday's always seems to do this. Between drinks, appetizer, main course, and primary server, you often see 4 different people. Who the heck gets the tip? That really p*sses me off.