that is so hard to answer as the older version has less bugs but also less functionalities, as they added a few functionalities then we have more bugs, at this point I don't know exactly, but i will have to check a few software version to see which one is best. a wild guess anything from 3 to 4 updates ago. but again not so sure and it will be really hard to detect all issues unless one is on the vehicle testing it. am currently using all the latest software but benz which I rolled back to 6.0. benz 6.0 seem really good so does bmw 7.10, Gm, ford and chrysler have a few issues but besides pats and immo and vin writing for chrysler, the rest is not so serious yet and although the layout is not the same it works for the most part. nissan can't do nats in many cases, there is just too many vehicles and function to be sure of anything, this has to be a team work if we expect to find them all.