The iPhone 1.1.2 Firmware just hit last night while you were out shooting drugs into your eyeballs, but here's what you need to know about it in the harsh, sober light of day. Long story short, you should wait until upgrading unless you're Gérard Depardieu.
Availability: As of right now it's still not available on iTunes (in the US), meaning if you really want to update you're going to have to manually download the firmware yourself.
New features: Foreign language support, including UK English, French, German and Italian. A battery status indicator in iTunes is all you get other than that.
Brick status: Jailbroken but non-unlocked phones are upgrading without any trouble. Jailbreak status: Supposedly jailbroken using an as-of-yet unnamed method, but not actually applicable (released) to any phones yet. Consider it not jailbroken for any practical use. There are reports of downgrades from 1.1.2 to 1.1.1, however, in case you accidentally update your phone and want to revert. This hasn't been available to the public yet, so don't count on it being a safety net for you.
SIM Unlock status: Users report their phones re-locked after update. No news on unlock yet from either iPhoneSIMFree or the dev team.
Who should update right now: People in the US on AT&T who need foreign language support for some reason (like writing emails in French or German or Italian), but don't need third-party applications. Everyone who actually needs foreign language support probably lives outside the US, and therefore need SIM unlock to use their phones. In that case, you should not upgrade until a jailbreak and unlock has been released.
What's in it for iPod Touch: It actually supports adding and editing Calendar Events natively, without a patch. Although considering that you lose third-party applications and jailbreak status in exchange for a feature that you could already enable via a simple patch, it's not quite worth it.
Thanks to Tuaw comments for supplemental info.