The most recent patch notes answered something I've been wondering about the "summon-from-anywhere" LFG system since I first heard about it: what happens if you get summoned into an instance and then you leave? The answer, apparently, is that you go not to the instance's entry portal, but instead you get sent right back out from whence you came. That's a bummer and a benefit -- unfortunately, you won't be able to use the feature to do any cross-world teleporting (leaving Violet Hold, for example, won't work as an extra hearthstone to Dalaran), but on the other hand, you won't have to stop what you're doing wherever you are.
In fact, porting in and out of any instances you run may change your positioning in the game completely. Nibuca doesn't see any need any more to leave a hearthstone in Dalaran -- that was previously the most central location for collecting daily dungeon quests and flying out to meeting stones, but with neither of those things necessary any more, you can park your stone anywhere you want. It'll be very interesting to see how movement patterns change after the new system goes live. I doubt Dalaran will be a ghost town (if nothing else, there will be plenty of people there sitting in LFG chat), but certainly the LFG is mixing up the reasons that a lot of people are hanging around there.
Patch 3.3 is the last major patch of Wrath of the Lich King. With the new Icecrown Citadel 5-man dungeons and 10/25-man raid arriving soon, patch 3.3 will deal the final blow to the Arthas. WoW.com's Guide to Patch 3.3 will keep you updated with all the latest patch news.