TightWind is written by Kyle Baxter. Stay Hungry. Stay Foolish.

So here’s what’s new in iPhone OS 4: multitasking, application folders, Mail updates, iBooks, and iAds.

Multitasking sounds good. You can double-click the home button, and a dock will pop up with all running applications. When applications are “running,” though, they aren’t taking processor cycles–it saves its state, and opens it up again immediately when you move back to it. For applications that need to do things while they’re not open, Apple has built several multi-tasking services for them to tap into. There’s background audio, so applications like Pandora can continue playing music when not open; VoIP, so Skype can receive calls and text messages; background location service, so applications like Loopt can receive location updates without running; task completion, so if you close an application while it is uploading a photo it can complete the process in the background; and fast app switching (mentioned above).

That’s big. Applications should be able to multitask without using as much power and processing cycles as merely letting them run in the background would.

It sounds like, though, that notifications are going to increase even more. These are already a problem. If you’re using another application and a notification pops up, you either have to stop what you are doing to deal with it, or dismiss it and go and find the application when you’re done. This is fine when the only notifications you receive are text messages and calendar reminders, but this hasn’t scaled with third-party notifications. It’s distracting and poorly done.

Apple didn’t announce a new notifications scheme to deal with this. That’s what OS 3 needed most, let alone OS 4.

Mail is receiving some great updates. Unified inbox, message threading, and the ability to open third-party attachments in their application.

“iAds” is, along with multitasking, the most important update in OS 4. Rather than unobtrusive ads, Apple is building interactive, mini-application ads. They showed a few examples; one of them was a Toy Story 3 ad that lets you look through characters, videos, and posters for the film, play a small game, and check local showtimes.

Jobs says they want ads that are interactive and have “emotion,” too. The ad concepts are interesting, and could be convincing–but this still has the same problem all mass-market ads have: they aren’t targeted to the user. Fusion Ads and the Deck work because they know what readers and users are interested in, and so the companies advertising are directly relevant to them.

Apple got part of it right–ads need to be meaningful and useful–but being relevant is just as important for ads to be useful. At this point, they’re still delivering ads, whereas Fusion and the Deck are more delivering recommendations than they are ads. There’s a big difference, and I suspect many developers would rather use ad services like them rather than iAds. There should be room for both on the device.

I’ll have some more thoughts on iAds specifically later on.

OS 4 is a solid update. Multitasking looks solid, Mail received some great updates, and iAds is an interesting, if imperfect, entrance into advertising. Nonetheless, Apple needs to address the notifications scheme. That is the OS’s biggest liability at the moment.