I bought an i5 stock version of Mac Mini 2018 two weeks ago, and I'd say I absolutely love it.
I love it so much that it became my main workstation the next day. Parallels works exceptionally well, and the macOS is exceptionally stable for non-power off operation.
So, I decided to return it and get the real big gun -- a topped off i7 version with 1TB of SSD, then replace its 8GB sticks with 2*16GB ones.
And today I got my new ones, returned my old one, and my nightmare starts.
THIS THING WHINES A LOT!
Basically when you are not doing anything, its coil whiles, a lot. Some say it's from the SSD section, some say it's from the CPU section.
I tested this with yes > /dev/null to force at least one CPU core to 100%, and the whine became much more stable, so I'm more leaning towards the theory that the CPU VRM is whining.
Don't know if it's from the added hyper threading cores (problem existing for all i7 units) or from just manufacturing defects of my own unit, but there're quite some users pointing out this bug.
Someone even made a video:
So all Apple perspective buyers, stay away from the i7 version!
I decide to live with it as I've already returned the old one and I no longer have a target disk mode device to migrate from, and Adorama won't ship a new one before receiving the old one.
Also, it will live on the lowest level of my computer desk, so practically I won't be able to hear it once I moved it down there, away from the bench top.