Yes, I have over-struck several types of coins. It can be difficult and a lot of work, especially when trying to strike a proof (polished) finish over existing coins that aren't proofs. It is almost impossible to strike out all the existing details on Eisenhower Dollars - some part of the design usually shows through. When I made Hard Times Tokens by over-striking Jefferson Nickels, the dies cracked the first time (but I continued to use them for a while).
Sometimes over-striking works out just fine, depending on the host coin type and the over-striking design.
Over-striking only a portion of the host coin (essentially counter-stamping) usually works ok.