It should not be too much different. i just made the switch a few months ago from speedball to pump woodsball... one of the best paintball decisions of my life.
-your first day or 2 may not be super exciting as you get acquainted with your new gun and the lac of firepower you now have.
- after you become comfortable with your pump you will find yourself focusing significantly more on the basics, snap shooting, accuracy, movements etc.
Like the ones before me said, when first starting out. you will double pump and shoot 2 balls, your pump stroke may be too short at times and you dont actually cock it back the whole way, you may pull the trigger multiple times without cocking it, because thats what your used too. but give it a day or 2 and youll be doing fine
as far as an A/T, many people love them, personally i cant stand them, i feel they are uncomfortable, and i feel like it takes alot of practice to keep accurate.
My biggest piece of advice would have to be----- DONT GET DISCOURAGED!!!! if you dont get a single kill your first 3 times out that doesnt mean pump sucks or you suck. it means you need to practice practice practice!!! dont give it up like alot of people do there first time playing pump!
and as for my last little tidbit. you will notice your skills go through the roof, snapping, accuracy, etc. because many times you wont be playing pump vs pump, and your lac of firepower must be made up with skills that you will aquire along the way.