I just bought a used 2007 Edge SEL AWD (35k miles), had it checked by our local mechanic shop (who were familiar with the issue and I looked under the car as well) prior to purchase - they said it was clean, but then about a week after we bought it, we had the smell as described in this thread (3 times thus far), and I took pictures and brought the car to the dealer and they confirmed a leak in the seal - but I think it's the axle connection to the PTU, not the driveshaft part. They have parts on order.
This website really has helped, and I will confirm what parts the dealer replaces. The Edge was garaged in winters, and only driven highway miles during summer by the prior owner...but we've driven mostly city w/lots of hills. Weird thing - it looked fine when we had it checked prior to purchase, then it leaked and smelled, but last week it hasn't been smelling or leaking (no new spots on garage floor....)
I like the car, and am hopeful that the leak can/will be fixed. Many thanks to all who have posted.....and good luck with your Edge's.