Well, it looks as if opinions are fairly evenly split. In the spirit of fair play, I'm going to join and give it a year. If I think they're representing my interests and doing the job well, then I'll continue. If not, I leave.
Having looked at the US AOPA site, they offer far more services and its a shame we don't get the same here but I take the point about the limited constituency they're calling on and its probably not possible with their limited resources.
Cheers.