Make sure you get the crank pully tool if its an auto. Other than that its a very simple install.
As far as acceleration I can't comment on exactly how fast, but overall responsiveness increases.
Do your research. I got the Perrin and haven't had any issues, but have heard of others getting a vibration while accelerating. Grimspeed seems to have a great product as well.
Just like any other car project make sure to include beer during and after the install. Also talk with your car. Let it know why you didn't think it was good enough and only want to make it better. It will boosts its self esteem when it knows you care.