Depending on how badly dented they are, they could make for a bumpier ride or adversely affect your car's handling. If you can feel a difference while you drive, this means your tires will probably wear unevenly if you don*t repair or replace the rims. Because I don't know how bad the dents are, you're in a better position to determine if they are affecting your car's handling.
Depending on the type of wheels you have, it may be less expensive to repair, rather than replace. A few calls to local shops should answer that question.
Be sure to maintain proper air pressure in your tires, which will help to safeguard against dents, in addition to helping your tires wear evenly.
〉 Answered on Jun 27th, 2008 by Denise Koeth, Managing Editor at Tire Review Magazine