I know other people have similar issues so I just thought I would add my observations.
Ideally I want the phone to automatically switch to WIFI when it's in range of my, or another pre-defined WIFI access points.
So, in the settings I've changed the priorities so that WIFI is above the T-Mobile 3G access point.
I've previously read that if you come home and you are already connected to 3G then the phone won't automatically switch to WIFI unless you disconnect 3G first by holding the red button.
When I do this however, if I try to access the Facebook widget it connects to 3G again. If I then try to cancel the connection I get into a loop of messages asking if I want to disable the Widget's access to the internet. Then, sometimes, I get a message saying there is an internal error and that I must re-start the phone.
I've also tried disconnecting the 3G, and then manually connecting the WIFI before then trying to access Facebook - in this situation the 3G just connects again and I then have both 3G and WIFI connected at the same time.
However, if I'm at home and I re-start the phone and then try and access the Facebook widget it sometimes asks me to choose which I access point I want. I can then choose WIFI which then allows me to open the Facebook application without it opening the 3G connection - however this doesn't always mean the application works because sometimes it says it can't retrieve any information once it's loaded.
Internet Explorer is OK because the application it's self has the setting to always ask which access point to use.
It's all a bit confusing!
The only thing I haven't tried is to remove the Facebook application from the home screen and see if that changes the way it behaves.
I do wonder though if the nature of home screen widgets means that they are designed for 3G access only, in which case I'd accept it but it does slightly annoy me that I know the phone can use WIFI for the widgets but I just can't work out how to consistently get them to do it!
Good phone though generally speaking, but pretty buggy - I've had to take the battery out a couple of times because after a crash but I still think I've made the correct choice not to get an I-phone! :icon14: