Apple released firmware 3.0.1 shortly after 3.0 to fix an SMS exploit that allowed hackers to take over your iPhone’s calling features and steal your information among other things. (Apparently, the exploit also managed to text your ex’s about how you could change, record the wrong shows on your dvr - so your stuck watching Saved By the Bell “The College Years”, and lower the miles you received per gallon on your car). Needless to say this reckless exploit needed to be stopped.
So why wait to upgrade if this exploit is so detrimental.

If you’ve jailbroken your iPhone and gone through a firmware update with Apple, you know how time consuming it can be to restore all your jailbroken apps (even with aptbackup and appbackup; when they do decide to work).
Jay Freeman (”Saurik”) also knows and is promising something, that I can only imagine to mirror what iPhone devs use to do with earlier firmwares 1.x.x; which is allow you to upgrade straight from your iPhone, without a computer. It may only be 3.0.1 specific, since there are negligible changes aside from the sms patch, but this could open the door to complete upgrades without iTunes.
I guess we will have to wait and see.
If you don’t want to wait, check out How to Jailbreak and Unlock 3.0.1
[...] firmware 3.0 to 3.0.1 except for an SMS exploit patch. If you have a jailbroken iPhone, read Updating to Firmware 3.0.1 (Why you should wait) before proceeding. Therefore, nothing really changes with the jailbreaking and unlocking [...]
