It's expected that they'll cost the same as the 3GS did when that came out, the prices they mentioned for contracts are the same. You're looking at £535 or so, sim-free.
No love from me for the iPhone 4. The actual hardware looks nice enough but iOS4 looks a bit rubbish. I couldn't give a shit about the books and video calling doesn't interest me either. Plus the fact that it only works with other iPhone's and over WiFi, it makes it easier to just use Skype anyway.
Longer battery life looks like a myth as well, the numbers are pretty much the same as they said for the 3GS if you look them up. Standby time of 300 hours actually IS the same figure they gave for the 3GS. I doubt there'll be much, if any, difference.
Good point on the battery life - the only thing I'd say to counter that is, if you havent experienced what Apple have done with the iPad battery, then you dont really know what they are capable of.
My missus brought a 64gb iPad Sunday, had a day off yesterday and was on it pretty much all day (damn you GodFinger and We Rule!) and I mean literally all day - about 11pm last night, she had 6% left and that was using Wi-Fi, speakers and with about 3/4 screen brightness. I'd conservatively estimate that she used it for 12 hours given the times we stopped to eat, watch TV etc. It really is a marvel and perhaps they can get that tech into the phone.
And the OS? Think despite its flaws its been proven to achieve what it set out to do. When OS4 is launched, multi-tasking will probably be the best benefit to most of the geeky people who follow these things.
To give you an example of the OS... last week, one of Claires friends came round for lunch, she's not very techy at all (still has an old Nokia phone) and never used an iPhone.
So she asked to see my iPad (as do all the ladies

), so I gave it to her to have a play with and didnt really say too much to her. Within 5 minutes she completely understood it and said "god, this is so easy to use - I might get one instead of a laptop".
At that moment, a 'BING!' went off in my head - as it must do for Steve Jobs when he hears it!

The OS does what it needs to do to drive some quite complex features under the hood, but on the surface, I'd say pretty much ANYONE could pick up and iPhone/iPad and be using it comfortably in seconds.
I agree that things that run on Android are probably nicer for 'us' in so much as we are more into customising and modding - having a bit of freedom - but as I've said before, to me, it makes the device feel a bit... messy?... as it doesnt have a standard like Apple does.
Still undecided.
I really like the Desire, but the battery, keyboard, lack of decent standardised apps and niggly bugs IS turning me away from it. Which I'm gutted about after only just buying it really. Probably will have to put up and shut up for now...