YankeeJim:
Topspin works for the fairway attempt to hit the green with your 2nd shot but can cause problems with your iron from layup position. Topspin=forward roll so it would actually fight the slope and run out of gas. Use back spin and hit past the flag to be sure of coming back.
YJ
It could be different for different clubs, but with the tour starter wedges, you will come off the hill with topspin if you layup on the 2nd shot. The ball hits the green, rolls up the hill, comes almost to a complete stop, and then begins it's slow downhill roll. If played properly, the ball will end up within a few feet of the hole (I haven't been able to sink it yet for bird).
edit: Of course, if hit too hard past the hole, you'll end up with the most imposing downhill putt ever.