Colleagues and I used the ALT for an all day business meeting. We chose the hotel only because we thought it would be convenient: people were coming from Calgary, Montreal, etc. and they could just get off the plane, walk onto the SkyTrain and be in their rooms minutes after landing.
I was not expecting much after looking at the website, but I was very pleasantly surprised when I arrived by car. Parking was a snap. Checkin was quick and flawless. The room was very high-tech and austere but perfectly functional for my purposes and very clean. We dined at the Sheraton, which is about 5 minutes away on the SkyTrain.
The meeting room was perfectly appointed. Again, austere, no-nonsense; all the electronics worked perfectly the first time and there was a tech there to make sure they did. Lunch was served by hotel staff and the food was first rate.
There is a buffet/bar arrangement on the first floor. I did not eat there but I had a drink and the surroundings were very pleasant.
So I would give this unique hotel 5/5 for business purposes. You could spend five times as much in a downtown hotel and be less satisfied. Also, you would have to incur the inconvenience and cost of getting downtown.
Of course, if you are visiting Toronto to take in the downtown sights, you may want to think again before staying at the airport. You could take the UP Express downtown, again by walking onto the little SkyTrain and connecting, but all of this would use up tourist time.
I would also compliment the staff, who were very efficient and personable.