Everything went well with one exception. (See below). Showed up on time. Very polite. They looked at the ductwork and diagnosed the problem. Showed me the evidence of mildew (camera pictures of duct walls, sample of duct wall cut-out). Cleaned and treated all the major ductwork. Cut out access holes where needed to get to the duct work. Resealed all of the access holes, as well as other leaks in the ductwork. (Showed me "before and after" camera photos of the holes and cracks in the ductwork. Sprayed a biocide the the duct system. Very complete job. Worked steadily and carefully. Took about 4 hours, which is what they had estimated. The one problem concerned the UV light installation. Not sure I really wanted it, but they sold me on it. I wish I had asked more questions before they installed it. Turned out it was a very small light that is installed in a hole in the ductwork, then sealed in place. The light runs off AC power, with a plug-in power cord like a floor or table lamp. The UV light is supposed to be on all the time. When I asked about the life of the bulb, I was told anywhere from a year to 3 years. I asked how to get a replacement bulb---was told I have to go online and order. I asked how to replace the bulb---turns out you have to pull the unit from the ductwork and then reinstall it after replacing the bulb. Doesnt look like a simple job. Plus, have to monitor an indicator light on the unit to check and see if its running. Means having to climb up in the attic periodically to check---I was told every couple of months. Finally, it was obvious these guys were not electricians. They plugged the outlet in to the same circuit that serves the overhead light in the attic. When you turn the attic light off, the UV unit goes off. To leave the UV unit on all the time, you had to leave the attic light on all the time. I didnt realize this until after they left. I fixed the problem myself by locating another outlet in the attic that ran off of a separate circuit that is powered all the time, and I plugged the UV light into that outlet. In my opinion, the workmen should have realized that their original hookup wasnt the right thing to do. If I had it to do over again, I would have declined the UV light and saved several hundred dollars. Other than that, I feel like I got my money's worth from the duct cleaning. The workers did a good job with that.