I have an 08 with around 30K on it and it only went into regen ONCE, that is right when I got home from the dealer. As long as you put it in high idle if it will idle for more then 5 mins you generally don't have any problems, as the exhaust seems to burn cleaner and not soot up the DPF.
I also see just over 20 MPG cruising at 120 kmh.
I just put a smarty programmer on it last weekend and it seems to have lots more power and just slightly better mileage.
As for the DPF I will probalby leave mine alone till the warranty is over then I will pull it off, that is the main reason I went with the SMARTY, it allows you to tune with or without the DPF.
I also have an 08 and have never had any problems. The truck now has 40,000km and i have never had it go into regen...it gets about 18-20 MPG at about 120kmh running 35" tires. I had an 06 with the 5.9 that got about the same mileage but never had the same kind of power towing as the 6.7 does...and that engine brake is the best thing Dodge ever put on there trucks for towing.