We have had Good Sam since we started full-timing in September, 2012. I know others have had worse experiences, but here are mine:
1. Flat tire on trailer on interstate near major city (Montgomery, AL) during a weekday. Called Good Sam, they indicated it would be around 45 minutes and that they'd call back to make sure that someone arrived. Someone arrived in about 45 minutes, Good Sam called just as they arrived. The truck sent from a mobile tire store had a jack that wasn't strong enough to lift our trailer, so he called back to the shop and within 15 minutes another truck arrived with an air compressor and heavier duty jack. Had us on the road with our spare fairly quickly after that.
2. Toasted bearing on I-40 in the middle of nowhere in Arizona. Good Sam indicated it would be about an hour before a mobile tech could get there. They did indicate that any repairs were on our dime (I expected that). Tech from truck repair shop a half hour away showed up when expected. Surveyed damage, drove to Flagstaff to get parts (new hub, bearings, brake backing plate), drove back (nearly an hour each way). Repaired wheel enough to get us up the road to the next town (where he came from). Took trailer into their shop next day and they put a new axle in (the end of the spindle was chewed up).
3. Another toasted bearing (related to incident #2) on a major interstate in Phoenix on a Saturday afternoon. Good Sam indicated that it would be hours, if not days (i.e. on Monday) before they could get something there to get a 40 foot fifth wheel somewhere. Good Sam tech asked if we were able to ratchet strap up the empty axle end and drive the rig carefully to a repair shop about 3 miles away. Fortunately, a good samaritan had stopped and helped me with the strap up, then followed us as we drove the trailer about 15 mph to the shop (on surface streets, fortunately).
Those are our only three incidents. One could say that they failed on incident #3, I guess, but they at least did offer some way for us to get off the road and to a safe place even if it involved me doing all the work.