If you order the ones from Lee Valley get a small bottle of fish glue to go with the plug cutters. The fish glue is water soluble so once you trim them down a little wipe with a damp rag will remove any trace of glue at the surface that could interfere with your finish.
Because the cutters are tapered, if the plugs break loose when you drill them they can be a little hard to get out but it's worth it because they don't leave gaps and if you can match grain they can be almost invisible.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.