The 3.0 update has made the GPS terrible on my 3G.
Before the update, it used to update Maps smoothly and precisely as I hiked trails or drove my car (dash-mount so the signal was good). I'd see continous motion, great for knowing when I was getting close to a turn or whatever.
Now it takes 30-60 seconds to get a precise fix, and until then it's way off--miles away. Worse yet, the map no longer scrolls smoothly as I driveit takes another 30 seconds BETWEEN fixes, and then it jumps. Nearly useless for driving, and it used to be great.
Google Earth on iPhone has the same symptoms, so it's Location Services that is to blame, not the Maps app itself. I'm convinced there's a bug Apple needs to fix.
(I also notice that typing is a bit slower, and the iPod operation is much slower: launching it is much slower, and starting every song has a second or two lag that wasn't there before 2.0. So it kind of seems like an overall performance problemexcept that demanding games do still play just fine.)