Can someone fill me in on the effects of varying saddle angle from perfectly level? What might be achieved by a slight forward tilt, backwar tilt, etc?

uh- numbnuts?

Seriously though, not sure if there is any advantage other than finding the correct angle that makes it most comfortable for you to ride. I think you may find that very small changes will have significant affect on how it feels. I find my saddle tilted nose up does truly make me numb. Tilted nose down I always feel like I am sliding forward and spending energy trying to maintain my location on the saddle. And I am talking a degree or two of change. No two people really have the same anatomy, so YMMV.

waterboy is exactly right. Personally, I like a few degrees "down" from level. To some extent, it depends on the design of the saddle as well. A cover that provides a bit more friction may let you stay in place a bit better, but too much friction makes it hard to move!

very true. But remember, the angle is also affected by the frame geomoetry, and handlebar setup as well. On my S-Works(comparct-road) my saddle is tilted downward a little, but on my Guru(traditional-road) its about level. I use the same make and model saddle on both bikes.

A well designed saddle (the Specialize Body Geometry Series is the "gold" standard) has a seating platform (the back half of the saddle) that is "dead" flat from front to back and "dead flat" from side to side.

And, there is only ONE correct position for a well-designed saddle: with the seating platform "dead" flat.

With poorly designed saddles, the back to front profile can look like a roller coaster. It starts out high, sinks, then rises again. There is no "level" part of the saddle to sit on, so the riders are always tilting these saddles up and down, trying to get a stable position.

Or, the owner of the bike has his bars set too low, which increases his "reach" and pulls him down and forward, putting pressure on the crotch. The owner tilts the saddle downward, which shifts him forward, closer to the bars. But, the saddle is no longer supporting the widest portion of his "sit bones".

The real solution is for him to raise his bars and bring the bars back closer to the saddle. Tilting the nose of the saddle down does not "cure" having the saddle too far from the bars, it simply conceals the problem.