I give this a 4 if you plan to walk up the mountain. It's a nice way to get a workout outdoors, but the slope is pretty steep, so ensure you are in good shape before attempting. If you haven't been to the gym in 6 months, then this will not be any fun. Depending on your fitness level, it can take 45 minutes to 1.5 hours. People often get competitive about the Grouse Grind time and you can see the best times of the day on the screen at the top.
To really enjoy Grouse mountain, try to go early or go during the week. The Grouse grind trail can very busy on week-ends and then, it is not nearly as enjoyable as you are either being passed or trying to pass slower people. Grouse mountain is conveniently located about a 25 minute drive from downtown yet will make you feel like you are far away from the city.
If you do go on a busy weekend, use the BCMC trail. It is not as crowded and brings you up to the same gondola as the grouse grind.
The only annoying part about the mountain is the gondola ride. You are often crammed in with other people and have to listen to someone trying to sell you all sorts of events and package at the mountain. The gondola ride down is also $10, so it is a bit on the expensive side.
Ensure you take in the views while you are on top of the mountain. With the amount of people in the gondola, you may not be able to see much on the way down.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.