Schwa:

New bushings would probably make the vibrations worse. Typically the aftermarket bushings are harder then the stock bushings, and thus they do not absorb as much of the vibration from the engine.

They should take that play out of your shifter though. They'll give you a more precise, tighter feel.

If your going to replace your brushings, I'd recommend you throw in a short shifter while you're at it, since you'll already have your linkage apart anyway.