We've been with the AA since 1996. We've had to call them out a few times over that period, and have been very impressed by their service - they've got us out of a few serious holes.
My DSis used to be with Britannia Rescue when she started driving and, like most of the smaller ones, we discovered that they just act as an insurer/middleman and call out a local garage to come to you - so you're heavily reliant on their skills, honesty, proximity and willingness/capacity to attend; compared with AA patrols who are already out and ready in huge numbers up and down the country, with the same training, no personal advantage in doing a poor job and their only job to attend to breakdowns.
She broke down once and BR sent out a bunch of cowboys, who did a horrendous botch-job; we later learned that their garage was notorious locally for watering down their petrol.
That said, the AA is not cheap at all. I just renewed a couple of days ago and it had gone up - from £227 last year to a requested £318 for this year! We have free 'gold' included home start for being with them for so long, but I think they stopped this for new members a while ago. I expressed dissatisfaction with how much it had gone up and she managed to knock £50 off it, down to £268, which was still high but a very welcome reduction.
We wouldn't be without them, but I would definitely recommend paying annually, if you can, and then phoning them/them phoning you to renew manually, so you can get the artificially-inflated price down considerably. Don't pay monthly, if you can avoid it, as they not only charge you interest but it also rolls over automatically, with no incentive for them to not hike the premium each year if you don't stop them.