I tried the demo 3GS in an O2 shop yesterday, and whilst it was faster, it wasn't £440 faster. It was great that regardless of how many tabs you have open in Safari, none of the pages need to reload when you go back to them. However, there was still a distinct pause on the 3GS when pressing the button to view open tabs, which is even slower on the 3G. Unfortunately, I didn't get a chance to see how faster typing in Safari was, which can be *really* slow on the 3G, so slow that it often misses out key presses and key press animations. I might have to go back into O2 and try a few forums to see how it handles those. I turned the 3GS off and back on again, and it seemed to boot up in about the same time, or slightly faster.
In Carphone Warehouse, there was a woman with a demo 3GS you could ask to demonstrate. I said my biggest peeve with the 3G was the speed, so she said we should compare. She got me to put my 3G on the table next to the 3GS, and she pressed to open the calendar on both phones at the same time. Rather embarrassingly for her, my 3G loaded the calendar faster than the 3GS. She tried it for a second time, and they both opened at the same time.
The slowness of the 3G is really just day to day things that I think are difficult to compare to the 3GS. For instance, at times, swiping to unlock my phone is incredibly slow, but sometimes it isn't. I would have to get hold and try the 3GS for a considerable amount of time to see if it suffered the same fate, or if it was as smooth as butter each time.