If you’re on 3UK, and want to use it on your iPhone with OS3.1, don’t upgrade yet!!! If you upgrade to a stock 3.1 direct from Apple/iTunes, it’ll lock your handset possibly forever – therefore you won’t be able to use any other Sim Card apart from the one it came with.
If you do want to upgrade to 3.1 (and still use any Sim Card) then I’d advise you hang off for the time being; yes it’s possible to do with the help of PwnageTool 3.1.3 on OSX… but you won’t have Tethering, a Carrier Logo or even according to the About Page – a recognized network.
The phone works on 3.1, and can receive calls and messages etc, but if like me, you like knowing that you are connected, and have signal (3G, Edge etc), then it’s a bit of a bummer not being able to see that info.
So last night, I went to the hassle of backing up my important data on the phone, wiping it all off then upgrading… to find the Carrier problem STILL exists in this PwnageTool release, then have to do it all over again back down to 3.0.1.
Ahh well; it’s not like I had anything else to do.