The hike to Haynach Lakes is just short of 17 miles round-trip. It's not terribly difficult, just long as much of the trail skirts a valley floor. The final pitch to the Haynach Lakes is the most challenging leg of the trail. This is Moose country, they tend to either be in the lush valley meadows or just in front of you - crossing the trail to get to the valley meadows.
It was a beautiful day, mostly sunny and a bit breezy, but a beautiful day to be out on the trail. Given the length of the trail the number of people you come across on the trail are far and few in-between - making for a very nice day on the trail. This is an excellent candidate for a multi-day hike.