I've had no issues with Safari apart from a "stick" keyboard in Landscape mode on occasion.
However, I had one massive lock up there just now.
I got a text message, so I slid to unlock, and when I tried to go into my Messages app, it just locked up. The messages app loaded, but no messages showed for a good 30 seconds. When I tried to read one, it highlighted that I'd touched it, but didn't open.
I pressed the home button and the apps "locked" off the side of the screen as they tried to meet in the centre ... the usual home screen animation where the apps zoom on screen from all sides?
I had to hold home and sleep and reboot the phone, and now it's fine ... nice and snappy again. This is the first time I've rebooted the phone since doing the iOS4 update though.