I had a GreenCine subscription for nearly a year. When I looked into Netflix a couple years ago, their indie and foreign selection was atrocious. GreenCine really does have a great selection of indie, foreign, art house, anime, and documentary stuff. The service staff is absolutely wonderful and the whole community bbs there is pretty cool too, and the user reviews and lists make the whole thing a little more involving than just an online dvd rental.
That said, I think part of what makes GC viable is where you live in relation to them. They have only one distribution center and it's in San Fran, I think. For me, on the east coast, this meant that movies took 4-5, sometimes more days to get back and forth. The 3-out plan costs 21.95 or something, so I was sometimes barely getting 4-5 rentals a month out of it if I didn't watch movies the day I got them. When I was watching a dvd a night and sending them in religiously the next day, it was great, but without that schedule, I found the service lacked the value for me so I cancelled it. Luckily I live about 1 mile from a great store that has tons of Korean, Japanes, HK, indie, cult, and just hard-to-find movies.
I'd definitely recommend GC if you live on the west coast, or at least closer to them than me and if you are going to get a large plan that lets you keep things rotating nicely.