The gorgeous new piece coming in Jan 2010 first announced by Dario here. The "Worldtime" feature is an alternative use of the central disk of the dial. The alarm disk carrries the major cities, with (in this case of the official photo) Paris corresponding to the triangle on the disk. You align the triangle with the hour hand, and you can read what time it is in the other cities of the world. However, this only works if you are in the timezone where the triangle is! I do not know if JLC plan to offer different dial options for different markets, e.g. Shanghai, KL, etc. Clearly that would be a good idea! (Of course you can choose to align any city as the relative time remain the same. London is 1 hour behind Paris etc) The downside is you lose your alarm time setting if you check a time - but you do 'interact' with the watch which has its charm.
So a good piece for checking international phone call timings in the office, much like the Geographic is, but arguably less practical in the field as a dual time watch where a 'Hometime' style watch is still better for this I think.