Besides a couple of the very helpful new features of iOS 4 like folders, multiple Exchange accounts, and unified inboxes, there are a few things I've been finding in my use of the new OS that are underrated, but very helpful improvements:
- In the iPod app, you can now edit, delete, and create playlists.
- If you plug the iPhone into a device which may cause interference, instead of giving you a vague popup asking you to put the iPhone into Airplane mode (which was almost always unnecessary), a popup simply says "there might be interference with this device," with only one button to dismiss the message.
- The Contacts app is much faster when searching an Exchange global address book. Still can't browse the global address book, though.
- Multiple apps/switching is really quite easy, and extremely useful. On top of that, it happens transparently—you don't feel the need to do anything extra to use this feature.
- 5x Digital Zoom works great with the camera for stills, but doesn't do anything for video (not like I'd want to do that anyways—it would result in pretty blurry video!
- The Photos app has been rearranged in a very good way—now you can tab through Faces, Places, Events, etc. directly, rather than having everything in one huge album list.
There are a few small quibbles I have so far, like Pandora's inability (so far) to run in the background—that will have to wait for an update—but on the whole, I'm glad I tried out the golden master preview of iOS 4 on my iPhone 3GS.