I'm currently on 3.21 Shop. I'm not exactly looking to jailbreak I'm looking at the differences between these firmwares and the retail ones. It's mostly just for learning purposes at this point as I have very little experience with the PS3 aside from many long hours playing games and watching netflix.
I do however have lots of experience with the PSP and wanted to get into this as well (somewhere in the distant future probly lol). As of now I know the jailbreaks don't work properly on shop fw anyway. Hopefully soon though, and who knows maybe I could have some hand in making that work! (Doubtful after seeing the insane complexity firsthand hehe).