You need to do the math as to how many times you will be visiting clubs vs what the membership costs. It may be less expensive to go with day passes.

It will also depend on which airports you will be flying through and on what airline. Does you little good for example to be a lounge member of a lounge in terminal 3 if you are flying most of the time from terminal 5 and they are not connected.

I think nothing great will describe most of the domestic lounges. It's way better than waiting at the gate, but there's nothing really that great about most of them.