I find these thread titles amusing, because this is just not the way that I think and work.
When I started getting interested in keyboards, I bought, found, or asked for many cheap, broken, and/or abandoned keyboards. I tested and used any of them that worked, for at least a few minutes (it was a long time before I learned that hot-plugging a PS/2 keyboard or mouse is dangerous - I had done it dozens, if not hundreds of times with no problem - I suppose I was just lucky) and evaluated what I liked and did not like about each.
Many (most) were given back, given away, dumped, or went back to Goodwill, some were sold on ebay, and some were kept.
The ones that interested me (for whatever reasons) were usually disassembled, cleaned, adjusted, and reassembled. That is how I learned about them - hands on. And yes, I screwed up and wrecked several along the way.
So, for me, asking me to list "criteria" in advance is strange. The way I know whether I want to keep a keyboard for daily use, or for my collection, is by using it in real life.
