I think a lot of cheap GPS products gave the CAA charts (which are IMHO the best VFR charts in Europe) a bad name, by displaying them on small screens, which is virtually useless because you can't see most of the airspace labels.
The smallest screen on which the CAA chart is readable is something like 8" to 10" - assuming 1:1 i.e. a real 500k scale.
I find they work fine on an Ipad, though the Ipad version of MM is a crap app.
Also I use the current-1 version of MM because in the last one they have somehow crippled the ability to run old QCT charts. With the version before, I can just drag/drop QCTs into MM's Documents directory using Iphone Explorer. This gives me access to potentially hundreds of 1:25k and 1:50k O/S maps which are widely available as QCTs.
For European VFR, Oziexplorer will open the way to running VFR charts for all of Europe, but the IOS version has been a long time coming...