One thing .co has been doing well of late, at least compared to new and many other alternate general purpose extensions, is promotion. Although a few links don't work, I really like their map where you can select a city or region and see some operational .co sites. If you are hoping to sell a .co locally nothing is more persuasive than to be able to point to a company down the street who is using one.
https://www.go.co/case-studies/
I wish all extensions did something similar. I think there are some markets for .co names, and average sales prices on NameBio support that the extension has value in many eyes, but it is certainly true that the types of names and potential markets will both be narrower. The registry holding as premium all short, unregistered names may in a way prop up prices for domain investors.
Bob