I'm more interested that 4.1 is supposed to fix the proximity sensor issue. It's a bit annoying when my cheek puts my calls on loudspeaker randomly. And I guess my sister who inherited my 3G would appreciate that supposedly 4.1 fixes the terrible slowness/lag of the OS 4.x.x on that ancient handset.

@itkj > short answer is no you can't. apple doesn't sign (i.e. activate) OS3.1.3 anymore. The only way to do it, is if you saved a certain file dump from your phone when it was on 3.1.3 - if you didn't, then you're screwed.

@everyone: iOs4.1 not supposed to be out already meh? google says sept8. but we're already sept9, itunes still says my 4.0.2 is up to date.

@battery discussion: for me, i'm disappointed a little with ip4's battery life too. not because it sucks, it's actually Ok at (for my usage) ~1.5 days. but because from the pre-release figures that i didn't probably digest properly, i was expecting at least 2-3 days.

well it's supposed to be the other way around i.e. 4.1 is supposed to fix proximity sensor problems on the 4.

all i can say is for sure 4.1 on 3G is awesome. not so much the features (there's like none for 3G), but at least the 3G is now somewhat semi-responsive.

haven't gotten round to updating my 4 yet (damn 500+mb download), but I'm also hoping it'll fix my proximity sensor problem.

@hcturtle could also be a problem with the usb cable. i've had that problem before turns out i changed usb cable and it was OK.