I use Sky Demon with paper backup.
Paper backup is also good for helping to give quick overall situational awareness, especially if you are using a small screen (as I am). You want your eyes in the cockpit as little as possible to ensure maximum lookout.
If you know where you were at a certain point in time, and then for how long you have travelled on a certain bearing, if a portable GPS device fails then you can still work out where you are. Hence why I write the time I reach a waypoint on the paper plog.
GPS jamming is becoming more of an issue - and there is often Notamed jamming near military areas. So you really want a non-GPS backup. Mind you - not everyone agrees with me!