Are mushrooms good for your garden? You bet.
Fungi in general are very important to soil health. By avoiding tilling, you don’t tear up the tiny mycellium running through the soil… and by letting things rot in peace, you Deepen the Awesomeness Of The Mystical Soil Web. Or something along those lines. I created a compost tumbler out of a 55-gallon drum (which sounds better on paper than it works in real life – you can read the whole hilariously stupid story in my book Compost Everything) and then forgot to tumble it for a while. An incredible flush of mushrooms was the result.
Fungi decompose what many bacteria can’t. Wood and paper fibers, for instance. If you see them in your yard or your compost, be happy. Good things are happening. The mushrooms you see, interestingly, are only the fruiting body of what is often a much larger organism. Tiny threads from one entity could be woven beneath the surface of your entire yard… only to reveal themselves as an occasional mushroom on the surface once in a blue moon.