I've done a few hikes in my time but I have to say that this one was the most arduous and difficult one I've ever done. Though its probably mostly my horribly cardio condition from sitting at a desk all day.
Despite the mild heat exhaustion, the payoff was well worth it. Its the most beautiful lake I've ever seen in the Cascades, ranking among the classics in the Canadian Rockies (Moraine, etc).
I didn't have the energy to walk around the lake to the glacier side, but I did venture across the haphazard logs at the outlet for a stroll.