Here is an example of how service has been lately for my wife and I. (We were not with the 4 kids, so it was a "quiet" meal):
After being seated, we waited about 7 minutes to have anyone from the wait staff greet us. We ordered drinks and an appetizer. 5 minutes later, came to take our order and brought dinner rolls. Finished those off, and our tea; I was getting ready to take a picture of my empty glass for this thread, when the waitress came and refilled my glass. Once this happened, I asked my wife if she wanted to take a bet on if our dinner would arrive before or after the appetizer.
Appetizer arrived, we talked and finished that off. Waitress took that (after we piled the app plates and the dish together for easy removal), then patiently waited for our meal. Manager comes out, and gives his speech about it is taking a little longer than normal tonight, and he was sorry. Then said there was a new cook and put the wrong sauce on my dish. Asked if we wanted a soup while we waited, we declined. Dinner was out before manager could be 10 feet from us (no reason for soup while we waited if it was that close). Person that brought food said again, new person in kitchen, blah, blah, blah. Waitress finally shows back up, never apologizing for the kitchen, we know it was not her fault, but could've been more PROACTIVE in letting us know. When I got the bill, not even our drinks were comped. I told the wife that I guess since we didn't take them up on their soup offer, we passed on getting anything in return for their mess up.
For taking so long on getting to us, taking a long time filling our drinks, letting us know about our order, and the amount of times she came right along the table when my card was at the edge waiting for her to run it, I still gave a 10% tip. The mess up in the kitchen was not her fault, but the others were. I had a hard time trying to justify 10% with the service we had.