I had them come out last May. It depends on what kind of stains you have to get out.
My friend used them a couple of times and she was very happy with the results. That's why I called them. My experience was not so great. I had a couple of areas in my off white carpet that my dog peed on. She'd sneak off when I wasn't looking, little snot. So I wanted those areas cleaned. I understood that all the stain may not be gone, but......
what the guy did was flood the area with some chemical that spread way out from the original stain and turn all my carpet a bright yellow. Then he sucked up the chemical and didn't go over it with water. I was mortified. A couple of days later I got out my own carpet cleaner and went over the area several times to suck up the yellow. I had them clean 3.5 rooms and 2 stairwells and it cost $500. I was extremely unhappy and gave them a bad review. The manager called me back and offered to come out again. Another guy did and tried to defend the first guy. I had the second guy go over everything again with just plain water. That worked, but a huge inconvenience. And no, it didn't dry fast. I had to keep a floor fan going 24/7 for a couple of days.
I'll rent a machine and do it myself from now on.