I'm sure I read somewhere that the v2.1 ones wouldn't work. I recently bought one of the generic Elm327 units from EBay, and although Carista could see it, I couldn't complete a download with it.
I figured it was worth the price just to go for the Carista dongle on the hassle front.
Carista is excellent - very easy to use. Not as many customisation options yet as OBDEleven, but I'm sure they will get there.
Si.
