Electronic flight computers are fine to use apart from the JAA ground exams HOWEVER......
If you decide to use one in flight for your JAA skills tests BEWARE.....
A buddy of mine went on one of his check rides and got out his shiney electronic flight computer. The examiner said "that looks like a nice piece of kit, do you mind if I have a look", my buddy hands it over to him to be told that the batteries have just run out and gets asked what he is going to do now!!!!
He didnt have his CRP5 with him and got failed for it!!!
Lesson being that the CAA really really dont like electronic flight computers!