Tuning is not magic, I actually encourage the owners to look at what is going on and learn. A good tune takes a lot of time ($$$ if you have to pay someone for all of it) and ideally if its a car or truck that is driven on the road, its not just done on the dyno. That is why I encourage the owner to learn. They can do a lot of it and end up with a better tune once it hits the dyno. Just for kicks on my own stuff I usually see how good I can get a tune just street tuning, then put it on the dyno to see if any gains can be made, and there always is some, but not always in the peak hp areas. The dyno with an eddy brake helps fill out the areas of the fuel tables on a street car that is very hard to get on the street. Its not just about peak numbers, that is pretty fast. Its about the data you are collecting, on the street your always having to shut it down and muddying up the data you need to tune, especially in the 3/4 -7/8 throttle areas of the fuel tables. On a street car/truck, fuel economy is important, so an accurate fuel table can help save money. Most mail order tunes are extra rich on purpose as its safe.
I have only been doing the dyno hauling for two years, but have been in the auto service industry since 1993. The first thing you learn with the dyno if your paying attention is most tunes have big mistakes in them and people never check. Its just the way it is. Recently I got called to help another dyno owner in the valley with a tune. The tuner was remote and only wanted three data points for fuel reference. The tune they sent back was horrible when it came back, pig rich, but the dyno owner did not care and the customer did not know any better. They did a few WOT runs printed out some graphs and called it good. It was not my customer or my shop so I was sort of unable to say much. I just tried to get the guy to take a second look, but was not successful.
I have HP Tuners personally, but its one that I am the least familiar with. I can not use it on the 96 c2500 as its not supported. A 0411 swap may be in the works especially if I do exhaust at some point, but right now it does what I need it to do as is. I have used MSD, AEM, Holley, TunerPro, and a few others. I actual want to learn more on the Megasquirt software as that seems to be the software of choice for a lot of the local drift and auto-x people.