Mounting speakers above (ceiling), bad idea?

[someguy03]

For my surround sound setup, would having my speakers (left&right, back left&back right) mounted on the ceiling and facing down at me sound worse than having them mounted at the same level as my head? Or would it be the same? I was afraid it would sound too much like it was coming from above when watching movies.

I am currently using a projector+screen for my home theater setup. I am moving it to another room in my house, and I would like to keep the surround speakers off the ground and off any shelves, which is why I ask. I don't mind having the 2 main floor speakers or center speaker on the ground, but I would like to have the left+right and both rears mounted above me on the ceiling (angled at me) to keep them out of the way.