This IMO is not as alien space bats as it first appears, the dinosaurs never developed tree dwelling forms and there is evidence that the primates were already evolving in the late Cretaceous. An upright ape wouldn't be that much more vulnerable to smaller predatory dinosaurs than to a big cat.
Basically, could humans and dinosaurs coexist on the same planet? How would they interact (dinosaurs don't strike me as being domesticable) and would their be any serious changes to the human species (but they still must be recognizable as humans).