Definitely worth it
I've been on GreenChip for just over one year, and it's definitely worth the price of admission if you're serious about advantage play. I'm not aware of any forum that has as many pros who are willing to share information on how I can make my game better. This year is the first year I've won money playing blackjack (mid 5-figure range) which is more than I initially thought possible after playing at best a break-even game for about 10 years. At least some of my success can be attributed to things I learned from the experts on GreenChip.
If you're a recreational gambler, play occasionally, and don't really care if you win or lose, then GreenChip may not be for you. However, if you're new to the game and serious about advantage play, I would strongly recommend joining GreenChip.