Just finished Leviathan. Pretty good DLC overall! I'd rank it as not QUITE as good as LotSB, but arguably better than all the other ME2 DLC's. And I was thrilled that they bothered to record new dialogue for all your squadmembers (and Cortez and Hackett, but unsurprisingly no new Joker stuff.) Wonder if they did it at the same time they recorded the new Extended Cut dialogue.
Oh yeah, one thing, making my post-mission rounds on the Normandy, I noticed Tali chatting with Garrus on the comm each time I entered engineering. Something tells me those chats existed in the original game (since it foreshadows the two of them hooking up right before Earth) yet there were never enough missions in the game before to give you the opportunity to hear them all.