Well worth a visit!
My car and I climbed over 5,000 ft from the Oregon coast to get to Waldo Lake in the Willamette National Forest. The drive along was well worth it. There are three campgrounds at Waldo Lake and North Waldo is the largest. I didn't have a reservation and attempted to find a site in the smaller two campgrounds first but neither of them had space available. Of the almost 100 sites at North Waldo I'd estimate that about a dozen were unclaimed the second weekend of September.
The campground was definitely crowded. There were many large groups with people of all ages. There was noise until about 11pm. Be warned that it gets VERY chilly at night. There are pit toilets but when I was there the majority were closed for maintenance and had been replaced by portable toilets. There are also water spigots and each site has a sump for dish water. The majority of the sites are removed from the water and only a select few are near the lake. They all have trees between the site and the water. The campgrounds also all have boat ramps and swimming areas. In addition to the trails throughout the national forest, there is also a trail that runs around the lake and through the campgrounds.
The sunsets are not to be missed! I spent all of my phone battery taking pictures of the sunset and didn't get any of the campground...