I've recently made a change in my setup and I'm wondering if there are any drawbacks to it. Specifically, I've taken my Ritchey stem with a 5 degree rise and inverted it so it has a -5 degree rise. I did this to lower my bars slightly, because I felt I was sitting too upright. My front end was a little high, probably because the geometry of my 2000 18.5" frame was likely designed for a fork with 80mm of travel, but my fork has 100mm.

Are there any drawbacks to inverting a stem? Will this make steering more sensitive/squirrely? The stem seems to have been designed to be flipped if desired, because the logo appears both ways, but is it a good idea to ride like this? I'd appreciate feedback.

The stem on my bike is flipped as well. I didn't notice any handling differences.

It can be done. All it does it pull you forward and down a bit. Would be good for climbing I suppose.

Probably. But (I might be wrong here) I thought the more rise your stem had, the more slack your steering would be. Hence the reason department store bikes typically have stems almost pointing straight up. Inverting the stem should make steering tighter then, shouldn't it? I suppose the difference between 5 and -5 won't be all that noticeable though. Not as significant as say 15 degrees to -15 or something.

5 degree to -5 isn't much. It will affect body position but should be negligable on steering.

The stem will not change the "slackness" of your steering. What affects the quickness or slowness of the steering is the headtube angle. The position of the stem only affects rider position. Cheap bikes with upright stems are to put the rider in an upright position which is more comfortable. Since the majority of low end bikes never see dirt trails, and are "neighborhood" bikes, most manufacturers keep the rider in the most comfortable position possible.

A lower stem will position the rider in a more forward position which will improve climbing ability, but hinder downhill performance. This is because the rider's center of gravity is lower and more forward.

The only drawback is if the stem is so low that when your handlebars turn all the way around, they bang into the top tube and dent/damage it!

L8R