Exactly - when I got my iphone 4 I couldn't believe how smooth/fluid it all was. I just wasn't used to it having only used windoze products where stuttering and lag is quite common.
Up to version 4.2.1 the iphone 4 was very smooth, with 4.3.x some of that feel has been lost.
Same thing happened on iPad going from os 3 to os 4.
The smooth feel was lost forever.