You see, before I upgraded my iPhone 4 to iOS 4.1, it sat on my desk with a lovely five signal bars glowing on its screen. Right now I'm lucky if I see four bars. It could be that Apple decided to alter how reception is measured and displayed on the device or that some sort of odd AT&T network hiccup happened at just the right moment and left me with crappy reception. Either way, it's not a pretty sight. Even if the signal bars are now taller:
The top part of the image is from an iPhone 4 running iOS 4, the bottom from one running iOS 4.1 beta.
That little tidbit aside, it appears that the modem firmware has gotten an update as it's now version 02.07.01.
As far as other issues go—the fickle proximity sensor in particular—it feels like there's improvement, but only time and more usage will tell if I can finally stop worrying about accidentally hanging up on someone due to a quirky proximity sensor.
Those are the only changes we've spotted in the iOS 4.1 beta so far, but we'll keep looking. If you spot anything yourself, feel free to send us an email.
Update 2: Whoops! Looks like there's a bit of an MMS bug in this beta. When you tap the thumbnail image of an MMS, you won't see the actual image enlarged but instead you see an all-black photo. The fortunate thing is that you can at least save it and view the full-sized image in the Photo app. [Thanks, Ruanne!]