I did the banks ecominder w/Data monster for a claimed +55hp +110LBFt on my 340hp (stock) Cummins isb 6.7 powered 08 Winnebago Destination and I couldn't be happier. Made a huge improvement in drivability, performance, and fuel economy. Hills like the grapevine that would drop me to ~48mph lightly loaded I now do at 60+. My worst observed EGT now is 1248F, after flogging it max power up a hill continuously it peaked there then settled down.
Returning from a cross country trip now I've picked up about 1.5 mpg average post tune and I'm not light on the throttle. I usually do 5-10 over.
As for reliability it remains to be seen, no observed increase in trans temps so I'm not terribly worried there. I usually set the trans in eco, the tuner at 2-3(out of 6), and leave it in cruise until there's traffic.
Imho the biggest reliability threat isn't the tuner or the trans, it's the turbo and the lack of a lift pump. I plan on addressing both. The EGR puking grime and sludge onto the compressor wheel is bad design. That VGT Holset turbo just won't last, stock or not in the factory configuration. I'm looking into options for that. I plan on adding a FASS lift pump and filtration to help out the CP3.
If anyone knows of an EGR solution for the medium duty 6.7 I'd love to know more. I know the SA engine tune has a lower EGR duty cycle, that probably helps some.
There are tons of performance and reliability upgrades available for the 6.7 isb unfortunately for us a lot of them are built around the FCA ecm. That said the cummins ecu is tunable; TS Performance does modify them..
Everytime pulling away from a stop now I just smile with the tuner set to 6 she really gets up and goes at city traffic speeds, at least for a big bus she has some moves now.
