Our kitchen has ceramic tile and the grout was starting to crumble in a few places and stained in others. We got a mailer which contained an ad for the Grout Doctor and after reading some reviews we scheduled an appointment.
The gentleman who came to our home (sorry, I don't remember his name but he had an Australian accent) noticed that some of the tile wasn't laying flat and I had been concerned there might have been a crack in the foundation. He pulled up the tile and said there was nothing wrong with the foundation it was just whoever had originally laid the tile did a lousy job. He was able to fix that up and now the floor is flat. We selected a slightly different shade of grout as the original was off-white and got dirty quickly. He worked quickly, cleaned up his mess and was very professional and courteous. The cost of the service was very reasonable. If you're considering redoing the tile in your home perhaps you should talk to these people first because they just might be able to fix your existing tile so you don't have to incur the expense of replacing it.