In the past two weeks, my wife and I stayed at 3 Clarion (Nordic Hotels) in Tromso, Trondheim, and Copenhagen. Of the 3 properties, this was our least favorite and it's very good but can be much better. I will say though of the 3 properties, this had the best dinner offerings that are included in the booking.
We had an overnight transit stay in Trondheim coming from Tromso and enroute to Faroe Islands via Copenhagen. First piece of advice, take the airport Flybussen service. A stop (Sodre Gate) is roughly 5 minutes away, download the Google Maps for this area and it will give you a very detailed drop off point / # of stops from the airport. Secondly, it's half the price of a taxi. When we departed, we thought with a 6am flight we had to be at the airport at 4am. No. There's a Flybussen at 3:54AM that picks up and will get you to the airport before it opens at 4:30AM. We opted for taxi and from hotel it's a fixed price at $77 (700NOK).
The hotel is within a larger structure that appears to be a mall and concert or performing arts center. Depending on the entrance you use, this can be very confusing and better exterior signage would help. Check-in staff was very straight forward and when asked about ordering a taxi for the next morning, she replied "you can do whatever you want." It wasn't exactly the most customer service oriented.
With 12 hour layover, we took advantage of its great location to walk 10 minutes to the Old Town bridge. The room was very large in comparison to other Euro hotels, but it was also set up awkward. No room view, we looked into what appeared to be mix office space and classrooms. Not an issue as we did not book the fjord room. The sheets were heavily starched, so much to the point my wife found the sofa and a comforter to be more comfortable than bed. We likely would have asked for new bedding or another room if we had more time here.
If we returned to Trondheim, I would consider this place again....however I would also be open to another hotel. There's some good here, but it needs some updating.