at some point in the past they were free, then to continue the normal service you had to sign up for a paid plan. So I stopped using their service. This is a "too little too late" for me as far as my customer experience goes.
Not sure what you mean. I'm a non-paying user from almost day 1 (oldest article from 2011). At no point was I forced to upgrade to paid plan. Did you use a third-party app maybe? Those only worked with premium accounts (http://blog.instapaper.com/post/3208433429)
Apparently that gets you downvotes on HN.