I've had one for the past 1500 mi. With 90% freeway driving, I've averaged 19mpg with A/C off and 18mpg with it on, that's going between 65 &70 mph.
I can definitly feel a power boost, and the 0-60 restriction delete is nice.
Hypertech's dyno chart shows 16hp and 18tq boost with 87 octane gas and 18hp and 20tq with 93 octane, not worth it for the premium I think. I use 89 octane in mine also.
What I'm disappointed in is you can't correct for different tire sizes and gear changes, or shift firmness. I've had a Hypertech in a couple of S-10s and those options were there.