I am. Spend some time in the desert southwest, particularly on indian reservations. You'll find that NWS temperatures are regularly off by 10-20°. But that's still better than Weather Underground, which can be off by as much as 50°.
One thing I will give the NWS credit for is the wind forecasts. Those things are spot-on at least 90% of the time.
I've lived in 15 cities in a dozen states, and what I've noticed is that if you're in a large city, or east of a large city, the forecasts are great.
But if you're west of a large city, or in a smaller city, it's hit-or-miss. This makes sense, as the better forecasters tend to end up in the larger markets.
Even smaller cities like Minneapolis, Buffalo, Sioux Falls, Albany, and hundreds more are located where they are because waterfalls and rapids made them the farthest extent of water travel before rapids or waterfalls or other hazards made the route too difficult.
Have there any been any comparisons of the commercial services to NWS? That would be an interesting casual study.
Edit: There are some additional interesting comments downthread: https://news.ycombinator.com/item?id=22740480