My wife and I have been to Murrieta's a couple of times on day trips to Canmore from Calgary. It is a great setting with a view over the main street of Canmore. We did not have a reservation and were luckily able to get in without a long wait (it is recommended though that you have a reservation).
The food was great and well prepared. One on of our trips we both had a steak (my wife is typically not a meat eater and rarely orders a steak) and both loved every bite. On our previous trip we ordered lamb and duck and we were both greatly satisfied with our meal.
The setting of the restaurant is a semi-formal atmosphere. It is a place you can come fully dressed up or casual as well (if you sit in the bar area). Costs for the main courses range from $20 - $40 depending on what you get.
We look forward to our next trip to Canmore so we can return to this restaurant which is quickly becoming one of our favorite places to eat.