The thing that would bother me is the lack of information on the Planet x website. There is a tiny bit more info out there when you do a Google search, however I would like to see them in the flesh so to speak. Aside from the lack of info on the mounting system for the front roller, I would love to know the exact sizes in litres as well as the dimensions of these. Modern bike frames come in a wide variety of sizes and buying online means you need to know the dimensions of the bags to see if they'll fit your frame or not. The front roller in the picture on Planet X's website is far too wide and is interfering with the braking and gear changing of the pictured bike.
Bike packing bags come into their own once you start heading off the beaten track and off road they are a far better solution than racks and panniers. However, this also means that they get shaken around an awful lot, so you need to be sure that the mounting system is secure, especially on the front roller. If your primary use is off-road, then bike-packing bags are definitely the way to go.