Tonight I pulled out my old iPhone 3G and decided to upgrade the iOS to 4.1. I was kind of disappointed in iOS4 as it made the phone run really slow. I have actually moved on from my iPhone and have purchased a Samsung Captivate (waiting for Froyo, but thats another story).
After some quick playing around with the phone it looks like some of the lag from 4.0 has been resolved. It was still kind of slow while trying to use the keyboard, but overall it has not hung up like before. I am not sure what I am going to do with this phone at the moment, but its another nice toy to have sitting around.
I will see how it operates as time goes by also, if I remember correctly at first I thought 4.0 was fast but after a day or so it would seem to be getting slower and slower. Wonder if that will be the same here.