I have written web applications in Ruby on Rails, PHP and recently Clojure. While I absolutely love Clojure and what it offers, building web apps with it has proven painful, because the library ecosystem just isn't there yet. There is indeed the foundation, as the author mentioned - Ring, the equivalent of Ruby's Rack, and a few other frameworks such as Compojure. But these are very early stage projects, parts of them are still being rewritten and they are relatively poorly documented as of now. If you run into problems along the way "how do you do this?" you would have a hard time finding adequate info online, whereas the amount of information that exists out there for RoR, for example, is incredible (message boards, tutorials, blog posts).

But even if you go through the initial pains of figuring out how things fit together, many tools are still missing. An easy to use templating library, for example. (several exist already but they are still early stages /are being refactored). Also things like the gems and plugins ecosystem in RoR - where you can pretty much find gems for so many things out there. (e.g.: tagging, authentication, etc). There simply isn't a comparison.

So, while I really love Clojure and I believe the community around it is growing - in both size and its contributions, I would say that, let's face it, writing full web apps in it right now cannot be compared to the productivity you would get in say RoR, due to the immaturity of the tools. That being said, I still see Clojure being immensely useful in other scenarios (for example: A.I. algorithms, high performance data processing, etc) and as such I would use it mostly in those settings, while integrating it with a more mature 'front-end' framework.