Just watching the webcast from slashgear.

First thing they previewed... Multitasking and it seems to be a very clever implementation of it.

They have provided an API of tools that will allow for background processes.

First one is audio streaming.

I imagine there will be many others.

These allow the processes to run without drain CPU power or battery life.

Skype running in the background will notify you when there is a call and you can answer it like answering a normal phone call.

Even when locked!

Very

Next, background location (i.e. sat nav or location updates).

Next, task completion Flickr uploads big photo and turns itself off after it finishes.

Cool! Folders for apps!

Think stacks in grid view on Mac OSX.

Woo!

SSL VPN support!

Makes it more likely that I'll be doing some dev in the future

Hmm it may be the first ever OS level support for advertising. I can see some developers pitching that wrong and their apps being bloody irritating.. The rest is all gravy though - you could probably summarise it as 'You know those things you complained about? We fixed them.'

Out for phones in the summer, iPad in the autumn. All features will work on the latest iPod Touch and iPhone 3GS. 'Many' features will work on the Touch 2G and iPhone 3G. I guess the initial Touch and iPhone get no lovin'. Not entirely a surprise. Odd that it's out much later for the iPad than the iPhone...

EDIT: Multitasking will only be available on the 3GS and most recent iPod Touch. I guess the rest get the GUI improvements and the updated Mail app. Oh and the adverts.

All a bit of a yawn for me.

I can't at the moment think of a reason why I would want multi-tasking, or adverts, or better mail (unless it has a spam filter), or enterprise features. I would use folders though. I could pop all my games into a game folder, nice.



p.s. Will it have a spelling chequer?

Oh I'll use the new mail app a lot. Threaded conversations alone is worth the upgrade. Pity it can't do rules based filtering though . Multitasking could turn out to be a big deal, depending on how it's used. For example, you can now have a game that plays multiplayer and allows you to talk to the person you're playing. And the ability to 'fork' processes will make a lot of difference to a lot of apps; you won't get the thing falling asleep while they're retrieving data for example. You'll see the spinner a lot less, I'd imagine. Presuming you have an iPhone 3GS, anyway.

We still didn't get printing (may turn out to be an iPad only thing; may possibly even be why the iPad version of OS 4 is delayed) and we didn't get the 'common file space' storage area that would get past the sandboxing of apps. Pretty much everything else people were suggesting we should get though, we got. Not a bad update overall.

Will there be any major reason left why a person may want to "jailbreak" do you think?

Also will this make any impact on the Google G1 (or whatever Google's phone is called.)

Unless I've missed something, the primary reason for jail (sic) breaking is to run applications not approved by the Apple Gestapo.
I can't see that changing.

It used to be to get it on to other networks as well. That reason is less of an excuse now.

Unless you have an old O2 iphone you want to use on vodafone (or similar)

I think there's an element of being able to say "I have a jailbroken iPhone" as well.

Can't wait for the launch of the next iPhone now! I've been on my contract for almost 18 months now and it's about to expire so I'll be shopping around for the best deals for my new iPhone!

Themes
A utility called SBSettings which is very useful - one touch access to things like turning wifi on and off, same for flight mode, GPS without having to navigate through the Settings and with it you can kill off any background apps and free up memory if it is running low.
I have a call filtering app on mine which sends withheld number straight to voicemail. Not approved by Apple which is a shame.

It will be good to know which features the 3G won't get.

Flight mode only requires two touches, Wi-Fi three.
I don't really care about the updates in this OS so much, I'm waiting for the iPhone 4G to see what enhancements are made in it.

Mark