I think this may be a new feature in CS only but you can now do healing and clone tool corrections on a new layer. Just do a Layer>New Layer. Click that layer to make it active and do the healing and cloning on that layer. That makes it easy to click it on and off to see the before and after or to dump that layer if you make a hash of it.
The beauty is you can add more than one layer and try different clones and then just erase or turn off the one you like least.

