But what about queuing for the lower level version at 90? I should be able to join a group of friends of lower levels and have the queue work, like it did in Wrath.
If the leader of the group meets the requirements (meaning is below level 90 in this case), I believe they can still queue you, especially if your group is completely premade. I'd have to check this though. We went back and forth on it. In any case, you can always just show up at the entrance to the dungeon the old-fashioned way and zone in.
In general, we don't want players using Dungeon Finder to queue for lower level content that is much too easy for them because then players who want to run the content at the appropriate level are faced with overpowered players who trivialize the experience, or pull aggro off a lower level tank, etc. We have no problem with you running lower level dungeons, provided other players aren't adversely affected.
Are Challenge mode dungeons going to offer more than just speed runs and a flat ilvl? I love the idea but I hopes it's more than just racing against a clock in an easy dungeon in the gear it's meant to be ran in.
At the Bronze level, you'll do good to just complete the dungeon in a reasonable amount of time, but you'll probably need to take it slow and stop and plan. It isn't just a test of who has the fastest movement speed. At the Gold level, you'll need to up your game even more and play smart as well as quick, taking risks where appropriate. The Bronze level is more like Heroic Arcatraz, Shadow Labyrinth or Shattered Halls when they were new. Gold level is more like a Zul Aman bear run when you didn't overgear the content.
That's the intent anyway. Nobody outside these walls has seen them yet so you'll have to let us know how they feel.
Are they actually tuned harder or is it the ilevel lock on them that is suppose to make them hard?
They are tuned harder. There are even some additional pulls and mechanics when necessary.