We went for Disqus in the end. I'm in two minds about it. In one sense, I think it's good to just get something up-and-running, but I really dislike giving such an integral part of our functionality over to something like Disqus.
The main purpose for having it is to add value for users so that they can ask questions about rates or certain blog posts we have. The other is to drive SEO.
Let's see how it goes. I'd prefer a proprietary option, but let's see.
Has anyone else had experience with Disqus?