>... I was getting good shots with my 18-55 using macro >setting. But I think they turned out lousy so that might be >the problem.
I doubt that's your problem, Nate. If you can frame the shot like you want it with your 18-55, I don't think a macro lens would give you better results. (Maybe more sharpness in the corners, though.)
Two problems you'll run into with macro is shallow depth of field, and the fact that because you're shooting so close to the subject any camera movement will be magnified and you won't get sharp images. The "solution" for the first problem is to go with a smaller aperture (for example, f16, or even higher), but even that may still leave you with too shallow a depth of field. The solution for the second is to shoot from a tripod using a remote shutter release to minimize camera shake.