"power drive" button on 94 ls

Hey all, I recently bought a a 94 rodeo ls,but it didnt come with a owners manual...I bought one on ebay about 1 month ago and it still hasnt arrived... anyway...Im still not sure how the "power drive" button works and when its appropriate to use it...I've used it a couple of times and noticed a big difference in the RPM's and accelaration. Is it ok to keep it on all the time, or is just used for those extra bursts of power needed? like say, when going up a steep hill?

I rarely use it here in Florida. I'll use it when I have to get on the highway. Just moves the shift points a little higher on the tach.