They aren't terrible, but at least some generations have significant fan clogging problems, and the fan is below the motherboard. They're also far from silent with the stock case. I would think twice before buying one.
I just went with a full tower several intake fans and a massive air cooler. This with a 65 Watt CPU, 70 Watt GPU and a 30 Watt GPU. The temps are only a few degrees higher than the M1 mini. It's definitely more money and more space than a NUC but it's nice to have a quiet environment. It is possible that I stick with Intel systems too. If they can do a few more die shrinks and come up with essentially a 10900 in a 45 watt package, then I don't mind keeping one around to run Windows x86 programs.