I put iPhone OS4 on my 3G yesterday. No big deal, everything looks OK. But overall it really doesn't seem like it adds a whole lot. I don't get the multitasking, so that's out. I get the folders, that works good. Ok, I can adjust the background of the screens. Everything else seems meh. Nothing I can really say is worth the 4.0 tag. Oh, yeah, the popup events are good, the way that they should have been.