It seems that in iOS4 the GPS updates are recieved with a 3-5 sec lag compared to the behavior in iPhoneOS3.
e.g I start changing my location and I only receive GPS updates after a few seconds. I stop moving and the location updates only stop coming after a few seconds. (GPS reception at its best. That's not the problem.)
In iPhoneOS3 there was no noticeable lag. You moved, you got a new location.
It's like Apple is making some preprocessing before propagating the results.
This is observed in my own code as well as in the default Maps App.
Can someone confirm this?