I drive with mine off sometimes around town because it's 45 mile speed limit is hendered by motorist that like to drive 35 instead of 45 but I would not leave it off at highway speeds for sure.
It's fine around town. It will hurt gas milege. Anytime your consistantly over 55 you should turn it on. It doesn't make the car any faster, it will just keep you in a lower gear putting you more into the powerband of the motor, and may not have to downshift.
Yeah, all it does is leave you in 3rd gear so you'll be burnin more fuel and using up more engine life(in the long run). It doesn't make your car faster or anything it's just there for towing purposes and such.
If I take my car out of OD, and I accelerate normally, sometimes the car acts like it was going to upshift into OD then it doesn't, there is a hesitation.
Now if I go about 1/4 throttle, the car won't do it, but less than that it seems to have a hesitation going into 3rd.
Seems like a factory programming thing to me. Maybe if you get a Predator or something and mess with the line pressure and shift points and such that could have an effect on your hesitation.