Hello from the Northeast!
First of all I think that Stanley Steemer does a great job for me on light colored carpeting, mostly area rugs. I think that it is a franchise so it all depends on who has good workers etc., but for me they are great. I've never had them do tile.
However, this spring I had my grout painted and sealed and I LOVE the results. Big kitchen, small hallway and 1/2 a bath which ajoins the former.It was $400. It has held up nicely for a hi traffic spot. Cleaning is a little different, the company recommends mopping with a sponge mop and then towel drying so that "puddles" don't just sit there and dry. The "puddles" actually have some dirt in the mop water, the water drys (evaporates) but the slight film remains. Changing mop water mid-way also helps.
I should mention that I have light beige 18" procelain tiles and off white grout.
It gave our kitchen such a snazzy look!
P.S. Towel drying sounds like a big project but all that is done is to put an old towel over the head of another mop and rub it on the tile. Swish, swish... Bravo-it works.