(Edit: Disregard this comment. Copyto has a fine business plan, a flat $1.99/month fee.)
I have a policy of only investing my time in a service if I know their monetization plan, to avoid getting burned by shutdowns or features moved to premium account plans. Does Copyto have one yet? I see no ads, the privacy policy is strict enough to make data-mining impossible, and there doesn't seem to be a way to pay.
Other than that, this looks great. It has all the features I use on Pinboard, and the thumbnail view could be handy.