I find F#/B/Db majors alright actually - the ones i have trouble with are the 3/4 sharp/flat keys (Ab, Eb, E etc.). With C major, F, G etc. you know that most of the notes, if not all, will be naturals (white keys); with F#, B, Db etc. you know most will be accidentals (black keys) - but with the sort of in between ones I'm sometimes left guessing as to which notes I should flatten/sharpen, and I find they are the ones that go wrong most often.
Ab Major is a pig of a key for me, but I sight-read the B major study in my study book...