I use Skydemon and mostly like it.
The only legal requirement I believe (SERA?) is that the chart is current (paper or electronic). In this case a properly printed paper chart from Skydemon would be more current than a paper chart bought at a shop that may be months out of date; I have heard of rampchecks where the paper charts needed to be updated with pencil before each flight to be current. Who does that?
What I like about Skydemon is the seamless integration with Notams and weather.
I would like to have the sector frequencies on the Skydemon IFR charts and have another symbol for tall towers.