We purchased our current house knowing that there was a bit of mold in the attic. We called The Mold Guy to deal with it shortly after closing, and they were here within a few days.
They showed up at 6am, because the attic can get quite hot mid-day. This wasn't ideal for us, but understandable. The work was completed by 3 men in 3-4 hours. They were quiet and clean throughout. They provided before and after pictures, which was very nice.
At the end, I was informed that there was _still_ a leak in the roof that I should have addressed ASAP - they saw damp areas. This was surprising to me (the sellers of the house told us it had been fixed, and our home inspector didn't notice anything), but was clearly true.
I was quite happy with The Mold Guy, although I was a bit surprised at the price ($2600 / 3 people / 4 hours = 216/h/person), but I'm not sure what the materials, travel, and other costs involved are. This might be totally normal for the industry. I would certainly still recommend them for their quality of work and the fact that they told me the roof was still leaking.