the only problem with using tensers as a movement method in 4e is that you can't shift with it. Since it is a special case (use a move action to MOVE(not shift) your speed)
So here's a question- pit traps
an illusionary floor would drop the disc, in fact, if it has the same function as 3e, would pop it out of existance because it got more than 3 feet away from the ground.
What about a canvas covering a pit? considered ground?
If not, what about a weakened floor?
As a DM, my answers for those two questions are- can it support the smallest and lightest of standard pc races (halfling)? If so, it counts as ground, if not, pop!