Yup, its out.  If you are not still waiting for your ipad2, its now time to jailbreak the iOS 4.3.1!  Win.  Now this is Mac only so, Windows users will have to wait, however, GreenPois0n RC5 is still good to go for iOS 4.2.6.  I will bet 4.3 support will come out soon.

BTW if you are having issue getting to the server, just be patient, it will let you in in time.

Instructions from Redmond Pie

Support for iPhone 3GS and iPod touches is on the way ! Simply follow the instructions below to jailbreak iOS 4.3.1 on iPhone 4 using a combination of PwnageTool 4.2, Universal Ramdisk Fixer and tetheredboot utility.

Here’s what you will need:

• PwnageTool 4.2
• iOS 4.3.1 firmware
• iTunes 10.2.1
• Mac OS X
• PwnageTool bundle for iOS 4.3.1
• Universal Ramdisk Fixer
• tetheredboot utility

Note:

• There is no unlock for the new baseband on iOS 4.3.1. If your iPhone relies on a carrier unlock, DO NOT update to stock iOS 4.3.1.
• iPad 2 users on iOS 4.3 should stay away from iOS 4.3.1 until further confirmation.
• Cydia is fully working on iOS 4.3.1
• It is a semi-tethered jailbreak.
• Your baseband will not be upgraded during restore process.
• Hacktivation is supported.

Modifying PwnageTool

Step 1: Download PwnageTool bundle (includes Universal Ramdisk Fixer) for your version of iOS device. Extract the .zip folder, in there you will find a .bundle file, for this guide, we are using iPhone 4 bundle iPhone3,1_4.3.1_8G4.bundle. Move this file to your desktop.

Step 2: Download PwnageTool 4.2 and copy it to /Applications directory. Right click, and then click on “Show Package Contents” as shown in the screenshot below.