I have been using the Boba 3G for a couple of weeks now and I have really grown to love it. I mainly carry my 19 pound 18 month old in it and find it pretty comfortable. I have neck problems and although it doesn't alleviate the pain when wearing it, I seem to be able to wear it for about 20 minutes without any real pain.
My 18 month old really enjoys the back carry in the Boba however I have tried using the stirrups several times and he seems annoyed by them,
My favorite part of the Boba is how easy it is to adjust the straps to fit me. I am under 5 ft and usually sharing a carrier with anyone is such a pain. The straps adjust so easily that I can get it to fit me in seconds. Way to go Boba!