We recently spent one night at the Delta Calgary Airport while travelling on business.
This hotel is great if you have an early morning or late night flight at Calgary Airport. It is connected by an enclosed walkway to the airport terminal, which is very convenient. It is also connected to the car rental lots. This is the greatest feature of this hotel.
Otherwise, it is quite an ordinary place - neither exceptional nor poor.
One positive is the dining selection on-site. There are 3 restaurants/bars in the lobby, and each are quite nice. This included one of Calgary's better known steakhouses.
One negative I found, is an $11 charge for use on the high-speed internet service per day. I find this to be unreasonable in a hotel that charges $150 a night and caters to business travellers.
Overall, I would stay here again, but only if I have an early flight like last time.