One cycle control looks very attractive. Anyone used this for PFC or general DC/DC?

I agree with Bob. It is a shame to have to scan patents before one begins a design. Also be wary of, when one views patents, any printed/stored materials can be summoned by the patent courts. Patents used to be used for a method of protection for an upcoming company, but now it is a big money-maker for corporations, even though they may not have directly developed the technology, but may have bought them.
In short, view, but do not copy (for very long) the patents.

Firmware is the new patent/copyright frontier. The differences are quite different. Copyrights are much more eternal than patents. My personal position, is that the over-use of patents/copyrights is stifling to the creativity of engineers..

Indeed, there are very strong patents on this topic. I used it in PFC control (Infineon controller). It works not better or worth than anybody's else PFC controller. I personally do not like it because it does not give me an access to internals (I use the frequency fold back with other controllers as well as other tricks to improve the performance). In DC/DC area this type of control is very effective especially for fast response systems. As long as you watch out for patents - the sky is the limit