My 12 lb 2 month old just started fitting them. They work just fine for us. We stuff with a prefold since my son can soak the microfiber insert quickly. I'd opt for the bamboo inserts if I were to do it again. The only things I have to compare them to are prefolds and Twinkie Tushes, so I don't know how they compare to other pockets.
I love my sunbabys. DD started waring them at three months, about 12 lbs. they fit great with the hip snaps. I always get a good fit. They are my daytime pocket, the size one are a little more narrow and slightly shorter rise than size two. I have the microfiber/bamboo inserts, they are good, I can't really complain about them. That said, I rarely use them, I prefer to stuff with a prefold, or just bamboo. Added plus they are super cute. Oh, and cheep, especially if you order direct they work out to about $6.50 each(shipped), you can get them from ebay but will pay more like $8 plus shipping.
Edited to add
I also have bg's and a blueberry. I like the bg's a lot, but I only have three and use them mostly at night or for daddy since they are hook and loop. I also have a blueberry, I don't like it, I just don't, no reason.
I really like the fit of them and they've held up nicely. Although I have noticed that the elastic starts to relax a lot faster than on our other CD's (Kawaii, Tots, Flips). We got a solid year out of them before the elastic started to give.
Re: Sun baby?