I can chime in with an anecdote about the first one on your list, RemarkBox [1]. We've been using it as the comment system on the Intoli Blog, and we couldn't be happier [2]. We first heard about RemarkBox from one of foxhop's posts here on Hacker News that we happened to see right around the time that we were thinking about adding comments to the blog anyway. We liked the idea of working with a smaller company instead of Disqus, so we got in touch and signed up to be what I suspect was one of the site's first paying customers.
The reason that I feel compelled to mention this here isn't that the comment system has worked well for us—although it has—but rather that it has been a real pleasure to communicate with foxhop and to be involved with RemarkBox at this relatively early stage. He's been extremely responsive to our feature requests, wishes us congratulations when one of our articles does well, lets us know if we forget to approve a comment, etc. Overall, it's just been a really pleasant experience. Definitely check them out if you're thinking about adding comments to your site!