I am absolutely in love with iOS4. I have an iPod Touch 3rd Gen 32GB with iOS4, and I'm loving it so much. Multitasking is amazing, better than ProSwitcher or Backgrounder. I also love how fast the freaking OS is. My iPod is blazing fast now. Folders is also much better than Categories. It's physically pleasing and runs perfect. (However, it stays open when you enter an app in a folder, which is pretty annoying) I love the little icon improvements too. Mail is amazingly awesome now too. I'm loving the homescreen wallpapers too. (Yeah, I know, winterboard can do that too.) iBooks is pretty awesome. I DL'd the iPad user guide and flicked through a few pages and was in love with it.