I have joined the PFA, although I don't fly a PFA type, and have less than zero interest in home building (indeed I would take a lot of persuading to get into something built in someone's garage). I joined for the reasons indicated by Genghis and others above and am glad that I did.
Having said this, the last time that this topic came up, I said that I'd go and join AOPA as well, for the reasons indicated above ie: that if we all join maybe it will get better. I didn't, so maybe I will this time.
PS: before all you homebuilders out there start strafing, I do realise that there are garages, and garages: I saw an RV 6 at Sibson last year which looked as well if not better built than my factory-produced aircraft, which it can out-perform as well.