I wrote this on the blog but will post here too:

I started to write an tutorial , almost finished it and I read the latest MuscleNerd's (Dev-Team) tweet:

"At the risk of sounding “mean”, everyone please stay away from sn0wbreeze until they’ve fixed it, or wait for PT, or just ignore 3.1.3."

So bottom line is , dont upgrade to stock firmware (iTunes) , for all of you that already have , no solution ATM.

Good to know (the BiggBoss and saurik notes):

Apple's TSS server stopped signing 3.1.2 today, so if Cydia does not state that you have 3.1.2 SHSH's on file yet you are now "too late".

That means those of you 3gs or iPod touch 3 users that did not store your TSS in Cydia or Rock are screwed and cannot restore anything but 3.1.3. If you are a jailbreak user running a 3gs or ipod touch 3 (or later generation ipod touch 2) that has not stored the TSS in cydia, you should be very careful with what you do from now until the next jailbroken firmware.
You will want to be careful in what you install to make sure you don’t have to restore for any reason. It would be a good idea to install open SSH and learn how to use it so that you can get in and fix any problems without a restore.