We came to Mallard Cove for a one-night stop on our way into Oregon and it was great for what it was. Very easy to find. There are a few sites (I'd say 4-5 max, unless you want to camp very close) that circle around a boat launch and a small dock. A few sites had fire pits, all had picnic tables, and there was a porto-potty and garbage cans.
Several houses line the lake, a few of which are within earshot (so be respectful). The lake water was full of thick algae when we were here, not great for swimming. In the evening smoke rolled in across the water from a fire that was burning in the area.
All in all, we were very happy to find this place. We came on a Monday in July and were the only ones here (aside from two cars that came down and left and one couple who launched their boat). It's great that places like this exist, take care of it as if it is your own backyard and hopefully it will be around for a long time.