I have found two issues so far with Safari and the iPhone 4. First, I have radio in my truck that has a USB input, I used to use my 3G to stream music in my truck to and from work. I can still do that with my i4, but when I click the home button after loading the stream in Safari it quits playing. I didn't have this problem on my 3G and the streaming works like it should on my Logitech Speaker Dock.

My second issue is with connecting to my work's wireless network. I am able to connect to it in the settings menu, but our network has a sign on screen when you bring up safari, that way we can control who (students, faculty & staff; i work for a university) is able to get on the network without having to change the Wireless keys. Safari doesn't even load the sign on screen. I get the message to accept or decline the server certificate, I click continue and then it kills Safari. This also worked on my 3G and it works our our Desktop Manager's 3Gs with 4.0.