I would agree with most the comments, here, that if you want to use a non-RCC lounge (recommended), and you have a layover > 2 hours, make the investment.
every time this topic comes up, i post in disagreement with the "card carrying crew" so i'll do so again.
-i don't have a frequent flyer card
-i hang in the same lounges as the rest of you
-i've never been denied entry to a *a lounge i was entitled to use