Update: Now that the 3.0 release is out in the wild, it only takes 3 steps

If AT&T didn't drop every other call we make and have the worst data service we've ever used, we'd think twice about dropping this little hint.  But we're about to unleash this with little guilt. Here's what you need to do to get Internet tethering on ANY iPHONE OUT THERE.  Yes, even yours.

So without further ado, the 9to5Mac Tether:

There are 2 things at work here.

A. The iPhone 3 OS GM activates on any iPhone as long as it is a legit iPhone.  (Not SIM unlocked and working on Tmobile in the US or Vodafone in the UK for example).  If you are using your iPhone on AT&T in the US, it unlocks without issue.  When you go to iPhone 3 you lose your abiity to Jailbreak (for the moment).  More information on this here.

B. The first iTunes 8.2 Pre-release (not the second) allows you to upload carrier .ipcc files directly to your iPhone which enables tethering AND puts your carrier settings on the iPhone.  This was a huge mistake (or was it?...hmm) from Apple because with this version of iTunes you can turn any iPhone into a tether iPhone without permission from the carrier.

This works.  It has been tried a number of times on a few different iPhones.  Here's the easiest way to do this:

1. You probably already have iTunes 8.2 final on your machine.  No problem.  Update your iPhone to 3 GM like so.

2. Now you have to download the 8.2 pre-release 1. We can't tell you how to do this but we're sure you'll get some help in the comment threads. You'll also need to get the carrier settings file from this application (UPDATE: Commenters are saying this one works better for AT&T)..  Most international carriers are supported.

Once you have iTunes pre-release1 , you'll need to completely uninstall iTunes 8.2 before installing the pre-release.

3. Completely Uninstall iTunes 8.2 Final by:
A. Trashing the iTunes.app application from your applications folder
B. Kill the iTunes Helper process in Activity Monitor.app
C. Go into your ~/Library folder and delete all of your iTunes plists and folders.  Alternatively, you can just create a new user account on your Mac and install it from there.
D. Empty trash

4. Install iTunes 8.2 Pre-Release.  Plug in your iPhone 3.0 and go to iTunes, go to the Summary page

5. Option-Click on Restore and browse to the AT&T.ipcc file you extracted from the iPhoneTether.app before (or here from AT&T).

6. Click open and you should only have to wait a few seconds while you see this:

7. Once that is complete, go to your iPhone/Settings/General/Network and you should see a new option about 1/2 way down called "Internet Tethering".  Click "on".  Instructions will be below.

8. Once enabled, your Mac should pop up a notification:

That's it.  You should be tethering, free of (additional) charge on your unlimited iPhone plan.  As far as we can tell, so long as you don't update your iPhone or iTunes, you should be able to continue.

By the way, AT&T doesn't allow apps like Sling because it considers the iPhone a computer and it falls under those terms of service - which is already a tethering plan.  If that is the case, then there shouldn't be additional charge for using your unlimited plan with a computer.

Boom.