I know that much has been made of data and connectivity problems on AT&T in the States, but I’ve found O2 to be just as bad, if not worse. About once per day, even though I have full bars and am connected to 3G, my iPhone is unable to receive any data. Loading webpages doesn’t work, refreshing mail doesn’t work, connecting to the App Store doesn’t work, etc. This occurs for about 5 to 10 minutes at a time and can sometimes occur multiple times per day.