I've looked at one of these at a lfs - they appear to me to be a "super" wet/dry, tons of surface area for bacteria colonies to grow, and a clever design.
For a person who wants to have a FO tank, with a lot of fish, want's to use a wet/dry, does not want to use live rock or live sandbed, and understands the pro's and con's of using wet/dry filter technology - I think they are pretty cool.
In a reef tank - or if one is wanting to maintain low levels of nitrate and reduce the need for frequent water changes - I don't see them as a good choice at all.
Neat design though. I'd be interested in hearing from "users" of this filter system as well.