Our first duct cleaning experience (we emigrated to Canada from a country where it's all water pipes and radiators) was excellent.
We researched into duct cleaning and narrowed it down to two suppliers. One appeared large and one smaller.
We exchanged Q&A by phone and email and found the large company employed people reading from scripts answering questions. Clearly high quality people and well written scripts, but you knew you were not talking to the engineer but the oily rag instead.
The small company, Ottawa Duct Cleaning, added value from the start by providing new and useful advice and info. The rest of the story panned out in the same vein. They arrived when they said they would. The crew were very hard working and neat and clean as a duct clean could conceivably be. They were also very polite and helpful when asked questions.
If I moved house and needed duct cleaning again, I would use Ottawa Duct Cleaning.