Not to say that I am an expert by any means, what I have been told is that you need to be VERY careful if you are going to use open source software to program your ECU. From what I understand it that open source software is more of a race application, ie tuning the car to a specific race track, straight away lengths for top end, evelation change, average corner speed / acceleration needs and so on.
The AP platform is a more rounded application that can be tweaked to a drivers style.... I would say the best bang for the buck.
If you wanted more out of your AP than stock maps there are a couple of different options. You can go to a local Tuner that uses AP (I have been talking to a AP Tuner in my neck of the woods).
There is a web version of tuning.
https://www.pdxtuning.com/services.htm I believe that you can get aftermerket maps based on your mods I think they alow for a tweak or two... They send you the maps... you do some data logging, send them the info and they will slightly alter the map for you. You would need to check with PDX with that issue.
Or Cobb has a street tuner software (not sure if it has been release for the 08) and you can do it yourself. Again, be VERY careful with this option
I am going with the AP in next couple of weeks. I then figured that I would then start to build up a libary of different maps.