A few days after upgrade of my 3G iPhone to iOS 4.1 I tried activating the Field Test. To my surprise it worked, but as you can see on the screenshot – not quite what I expected. It seems that 3G’s baseband is not supported, or the Field Test app is not yet ready. Either way, it is a good sign, that Field Test is back. Too bad is not really useful, at least on my iPhone 3G.
Besides that, iOS 4.1 speeds up a lot the old good iPhone 3G. Both springboard and menus are much more responsive – it works just as fast as 3.1.3 did (finally).