"LeChucks Revenge: Special Edition is official! New puzzles, new enemies, new hair!"
New Puzzles? What?
And... is there an announcement Three?
Update by Jason: While clarification of the features will no doubt come in the morning in the form of a press release and an official site launch, it's been confirmed that, like with Monkey Island 1, there will be full voice acting, and the original game will be included. "Developer commentary" has bizarrely been alluded to as a bonus feature - who knows what that means, but Tim Schafer and Ron Gilbert were on-site for the announcement. Also, here's the cover art.
Further Update by ATMachine: According to LucasArts' Twitter feed, MI2:SE will feature voice acting both in the high-resolution updated-graphics mode and in the low-res, original-graphics mode. Plus, Guybrush's hairstyle has been changed, so hopefully there will be fewer complaints about that this time round.
Update 3: According to LucasArts, MI2:SE will be available for PSN, XBLA, Mac, iPhone, and PC.
Update 4: This Joystiq article suggests that the game will be released "this summer." Also, there will be a new direct control scheme implemented in addition to the previously used point-and-click method.
Finally, it notes this about the extra content:
"They've also added never-before-seen art from Peter Chan and Steve Purcell and developer commentary (!) for you Monkey Island fanboys out there (that's you)."
Update 5 by Jason: Official site launched and here's the press release.