I'm probably going to break rank with the troops here, but I resort to AP when I have to if Katie desperately needs sleep. I try not to make a habit of it - limit it to one nap per day and try to use a different method of AP - so that she won't become used to it. But, we had a bad, bad day yesterday. DH had to come home early and I was in tears and having a couple of glasses of wine. (Neither helped, BTW, that's how bad it was.) Today, cuz of errands she had a very nice long morning nap and the afternoon was pleasant. Afternoon nap was terrible and now the evening is falling apart...but at least we made it this far.
Your sanity is important too. If you get a good day (or even a few good hours), it can change your whole outlook. So, if a little AP helps, do it. But, know that if a habit develops, you'll have to break that later.
One thing that I try to do before resorting to AP, is get Katie into her crib - at least for a few minutes, so that part of the routine isn't lost.