I love the mini computers, and I have a super mini, as my main blogging computer.
This thing measures under 3x3 inches, and is very powerful. However, it can put out 60w of heat, and the little fans are always running. I have a 4x4 that is quieter. Anyway, after a year, the fan was getting noisier. I took it apart and flushed all the cooling surfaces with contact cleaner. It uses a liquid coolant.
Much quieter how, and the fan runs steady. I don't know if I'll go to this size again, or get something a big bigger, with more passive cooling.