Hots and Dots actually has a long take on the Dungeon Finder, including "15 Things You Should Know," like that tanks and healers are still as important as ever (if you sign up for DPS and another role, you likely won't be doing DPS), and that we're finding out very quickly just how skilled or knowledgeable people really are ("the Party Leader will be forced to confess midway [through] that they actually know nothing about the instance").
On the forums, players are generally ecstatic, with lots of folks crediting the new system for bringing their excitement back into the game. Not that there aren't a few quibbles -- players say it would be nice to clarify if you want a brand new instance or a half-done one, and while GC says it wouldn't be hard to install, they aren't sure how that would pan out yet. There's at least one weird bug floating (or falling, as the case may be) around as well. A few players say that leaving the Oculus in as a random choice of dungeons is another bug that needs to be fixed, but I'm pretty sure that's working as intended.
But aside from those few quibbles, the Dungeon Finder seems like a hit, and it's definitely true that finding and getting a pickup group rolling is much, much faster and easier under the new system. Seems like the Dungeon Finder has lived up to expectations and then some.