Has anyone experienced a very slow, sluggish iPhone after doing the new 4.0 update?

I just did the new update for my iPhone a couple days ago. It is so slow now! It types slow, it’s very unresponsive, and for some reason I can’t use the Internet anymore if I’m on a phone call. Just to unlock my phone, it takes much longer than it ever used to and everything is very choppy. I’m so unhappy with my phone now. I hate the update and I want to go back to the way it was. Is it possible to restore the phone? Or downgrade? Any advice is appreciated!