My sister is looking for something to clean hardwood floors. She needs something that will REALLY clean as this is for her business.
I was thinking a steam vac might be the answer, but I know nothing about them.

Do you use one? Are they any good? What's good.. or bad.. about it?

These are not smooth floors, but have seams and lines in them to make the look old. Some of them, I believe, are actually plastic made to look like wood. They sure don't feel like wood and it's hard to get the stuff out of the cracks.
(Think very dark faux wood with white specks of paint all over and in the cracks.)