I'll list out a few cons however I still use it because of the value.
software is ugly, doesn't scale properly on a standard non full HD screen
doesn't have AFR/knock/injection duty/etc overlays vs. load points
USB port is flimsy, I snapped mine off had to resolder it back on
not full sequential, on a 6 cylinder it runs as semi sequential injections/semi batch firing (pairing 2 at a time)
once in a while it decides to write erroneous values to your ignition table
base maps are horrible, you really need to spend time on it to get it to idle, drive normally
however, once you sort out those small idiosyncrasies it works like any other ECU and the support is from the man himself unlike bigger brands they would just brush you off. Andy replies to e-mails at any hour of the day and weekends when he has the chance.. so thumbs up there!