I noticed it right away mate, and I thought I was being a little pernickety until I noticed more people cropping up in threads here and especially on the Apple discussion forums.
If Apple had added features to iOS 4 over the 4.1-4.3 updates which would explain degraded performance, then fair enough, but Home Sharing and Personal Hotspot are the biggest new feature in the iOS 4 updates, and I don't honestly don't think for one second anyone is stupid enough to believe either impact the way the iPhone UI animates.
Anyway, I've restored to 4.3.2 via iTunes and while the stock apps run perfectly, the real test is when the device has a load on it, so I'm going to install some third party apps and see how things go.
Here's an advance hint ... it'll be the exact same as 4.3.2.