Was actually really surprised when I didn't even have to do Bluetooth negotiation
The feel of the keys is beautiful, it's exactly what I want
The trackpad is more sensitive than the Apple Magic Trackpad. This is a good thing, since on Linux the Magic is way too slow.
The most annoying thing so far is that it makes a weird bouncing, twanging noise when I type, as if something plastic is vibrating against something else. This is not what I want from an expensive keyboard.
The reason I didn't go for an Apple keyboard was the stupid delay they've hardwired in to Caps Lock. Since I use Caps Lock as a Control key, that means I'm slowed down when editing text. This keyboard doesn't have that problem.
Another bug in the Apple keyboards is that Caps Lock + Shift + Tab doesn't send an event. The TK820 does, so, yay, I can switch tabs in my browser again.
Fn + Caps Lock is Scroll Lock. OK.
It doesn't use Synaptics on Linux, so I've got no idea how to invert scrolling
Fn & Ctrl are swapped from the Apple keyboard layout
Arrow keys are less far to the right
My right hand wants to move further right to reach for the Trackpad