New 4.0 update has ruined my iPhone

Why didn't Apple worn people that the new update was goin to trash the 3G phone??? Mine has not worked right since the install and I have heard this complaint from others as well. I have an 8gig 3G, and since the install, EVERYTHING IS SLOOOOOW. Aps take forever to load, texting is too slow to keep up and is difficult to use and takes forever to load up!! Very annoying. I paid good money for this phone and now it doesn't work like it should and Apple just tells me that they are not surprised and that they don't know how to uninstall the update and go back to the previous update. Thanks a lot. Any ideas short of "Sorry we(Apple) screwed up ur phone. Guess you will have to fork out the money for the new one."?????