It's an iPhone 4, on O2, model MC603B, running iOS5.1.1(9B206)
Since Sunday I have connected to my home wifi (Orange), paid-for wifi in a Travelodge, free O2 wifi in a pub on several different days, free wifi in another pub I'm now staying in (bt) and bt wifi in my Dad's house. With the Travelodge wifi I had to login each time before using it, but the connection was there straightaway, and it picked up the O2 in the pub immediately each time (after my first login)
When I arrived at the second pub last night it picked up the wifi immediately (I've stayed here before and it remembers the password each time) and switched to my Dad's wifi when I arrived at his house, and back again to the pub when I came back. No problems at all (except when my sister accidentally unplugged my Dad's bt box!)
I've never updated mine, and I've had it well over a year. Never updated any of my others either. I haven't got any problems with connecting to my wifi. In fact I never have any problems with it, possibly because I don't bother updating it?!
I had this very problem! I couldn't D/L it without being connected to wifi. I googled and someone said it was the case they had on it. I took my new (very cheap Hennes) case off and hey presto. I connected to my wifi. Very strange considering wifi can travel through concrete and metal
Oh, and I now have iOS6 and haven't noticed anything different yet...