We’ve been playing with iPhone OS 4 for a while now and here’s what we’ve learned: * It’s pretty stable, especially compared to other developer editions of the iPhone OS we’ve messed around with.
We haven’t had any crashes so far, and things seem mostly to be working. Find My iPhone doesn’t work, and iTunes 9.1 doesn’t know about folders and will delete any you’ve set up, but nothing major is broken, at least as far as we can tell. * The multitasking system works as described, but without any apps that support it it’s hard to test — we’ll see if we can cajole a copy of Pandora or TomTom to play with. Steve might say task managers are a sign of failure, but you can certainly delete icons from the switcher — just long press on them and a minus arrow pops up. * Bluetooth keyboards are going to be the next greatiPhone accessory gold rush. Been jonesing for a million-dollar idea? Here you go: slider keyboard case with built-in extended battery.
We prefer our royalties in cash, please. * We couldn’t get threaded messages to work in Mail, but we’re sure we’re doing something wrong — we’ve never really gotten along with iPhone Mail. * The zoom control on the camera is pretty slick, and there’s okayish macro. Tap-to-focus in the video mode is also a nice addition. * Spell check works just like the iPad, as do cut/copy/paste hardware keyboard shortcuts. Still no way to bring up the soft keyboard from the device when it’s paired, though, which is annoying if you walk away — you …
source : http://www.ngasal.com/index.php/gadget/apple-iphone-os-4-0-developer-preview-hands-on.html