yeeah i got the auto tune....
i would definetly buy the o2 sensor....it makes tuning MUCH easier as you can log your AFRs....
the auto tune feature is pretty good tool.....but it doesn't replace tuning....it just helps....basically you do a couple pulls with the auto tune on...then you take a look at your maps, smooth them out....
the 300 or so $ spent on the o2 sensor is worth it....