I kind of have mixed feelings about trans tuning as well. I understand that these tuners usually have a big r&d expense. I also feel some of the big name tuners are just glorified box tunes.
To the op (I've never ran his tunes) but look into pitockagtech.com. He is an enthusiast that writes a few tunes using the mm3 platform. He has a g56 truck which I feel is important due to some bugs that need to be worked out when changing gears. I talked to him a bit on tuning our cab and chassis, which I havnt done anything to it yet. He starts from scrach and writes his own base file. He claims his tuning is clean and trys to get good mpgs out of it.