As a controller, this can sometimes be difficult to assess. I've signed one as unsatisfactory for airmanship when safety was genuinely compromised but I've had a few who, in my humble opinion, have scraped through. There are no official guidelines for Controllers as to what 'satisfactory' airmanship is but we seem to get an awful lot of people who get lost, join for the wrong runway/circuit direction or use abysmally poor RT. I'd estimate having spoken to maybe a dozen students this year who have cocked something up on the QXC, but in most cases, I've been able to point out the error of their ways in a constructive and friendly manner and after consultation with their instructor signed their forms. I suppose this could indicate that some students are being 'let loose' without adequate training and I'm often surprised by the weather conditions that some qualifiers are sent off in. There does also seem to be some 'mystical' air about the QXC and lots of people seem to get uneccesarily worked up about something they should be capable of achieving without substantial difficulty at that stage of their training. Relax, enjoy it!