Free upgrade for iPhone 3GS users.

Starting on June 21, 2010 users who own iPhone 3GS devices can get the experience of the new iPhone 4 without having to purchase a new phone.

Simply plug your iPhone into your computer and do a Sync with your iTunes account.  (note: you will need to go through the iTunes update before downloading the new iPhone software.   See below for new iPhone software features from PC World.


Smart Folders
As simple as it sounds, this feature was missing on the iPhone. The folders feature in iOS 4 will help you declutter your home screen, letting you compile under a single location up to 12 applications.

To access folders, enter customize mode (tap on an icon until all icons start jiggling), slide any icon on to another and a new folder is created. You can rename the folder to your liking, but iOS 4 will also suggest a folder name if applications grouped in a folder belong to the same category (like games, utilities, travel).

Wallpapers everywhere
iOS 4 lets you set a wallpaper not only for the lock screen (as previously available), but also for the home screen. Like on the iPad, you will have the option to select a different image for the lock and home screen, or you can use the same image throughout. There is no way to set a wallpaper for each of your home screens, though.

E-mail improvements
The first thing you will notice in the Mail app in iOS 4 is the unified inbox. Users will multiple e-mail accounts have been longing for this feature for a while, and Apple finally delivered.

There is also support for threaded messages, so you can easily follow up on conversations (each discussion has a single entry that you can tap on and expand it). A big boon for business users will also be support for multiple Exchange account, as only one per device was available by now.

Spell-Checker
Alongside the predictive typing on the iPhone, spelling corrections were missing, but this issue is resolved with iOS 4. Misspelled words will be underlines with a jagged red line, and when tapped correction suggestions will be displayed. This feature works system-wide, including in Mail and Notes.

SMS search & Character Count
You can search through SMS messages in iOS 4, just like you do with e-mails in the Mail app. Just flick the top of the main messages screen and a search bar is revealed. A character count while typing a message is also displayed, so you can keep tabs on your SMS allowance.

iPod Playlist Creation & Editing
iOS 4 bring a few enhancement to the iPod app as well. You will be able to see a new music control bar at the bottom of the screen when listening to music in the background. There is also the capability to create and edit playlists on your iPhone with iOS 4, which get synced with iTunes when connected to your computer.

Orientation lock
The iPhone screen won’t annoyingly rotate any more when you are laying in bed reading on a side. The new OS brings a software orientation lock feature, which you can access by double-tapping the Home button and then swipe to the left (the same way you access the iPod controls).
See more at PC World: http://www.pcworld.com/article/199380/apple_iphone_ios_4_arrives_10_reasons_to_upgrade.html?tk=hp_blg