I am a member and although I don't honestly know the extent of what they do in terms of push or influence directly (as compared to the 2nd Amendment Foundation or the NRA and NRA-ILA), I get frequent packets of updates showing that they are "doing something".
As was mentioned above, a lot of the packets contain form letters with my various Reps and Sens on little post cards to send.
I have read that they are not very "transparent" in terms of their finances, but, again as is mentioned above, $20 isn't too much for me. They do seem to be at least active in trying to get members such as myself to be active in contacting gov't representatives.
Some things they send I deem superfluous and trite and even knee-jerk reactions, but others I find legitimate.
So as can be seen in my Sig., I try to donate and be involved with as many groups as I can afford. My few dollars being a member of a few 2nd Amendment-promoting groups is not as important as any actual "active" participation, whatever that may be.
I personally believe that me taking as many people who have never handled firearms to the range and teaching them everything I can on safe and fun handling and shooting and the importance of the 2nd Amendment as I see it, is probably even more important than $20 here or $50 there that I spend on being a member.
And don't ever forget to vote! (and encourage fence-sitters to vote as I do)