I am with IO540 here. I uses flitestar IFR extensively. Once you have worked out how to use it, it is a very powerful product indeed.
I like Navbox but it is only a VFR tool and Jepp does everything it does so I stopped updating it and stick with a single product. Jepp also integrates Jeppview so I get IFR plates direct in Flitestar and now they are offering the complete Bottlang set in the same way. A one stop planning shop!