Syntace makes some beautiful short stems in +/- 6 and +/-17 degrees.

With a too short stem, one can encounter "steering wheel effect," in which the steering feels vague and overly responsive at the same time.

I know that sounds like a contradiction.

Steering wheel effect shows up more with steep head tubes and less with relaxed head tubes.

On my Pista, with a 75 degree head tube, I need a 75mm stem or longer.

My Karate Monkey, with a 72 degree head tube, feels great with a 60mm stem.

I hope I haven't made an inaccurate generalization, above: the Pista has 23mm tires and the Karate Monkey has 60mm tires, and tire size can make a big difference, too.