I have to back IO540 up on this one. I was reading through the practical test standard for the JAA CPL the other day and was smiling. The level of experience expected is much that of an FAA PPL.
Not saying that the flying is any better or worse either place - but I'm pretty confident that if you pass the FAA ones the JAA ones should at least not be any harder.
As an exampel I can say that the school I'm with at the moment does (or used to do...depending on how you look at current events) both JAA & FAA training, and the first time pass seem to be very high for the JAA examinations.
Further a friend of mine now flying for Mesa Airlines (USA) did his conversion with OAT saying the same. JAA theory is a b****, but the flying is a piece of cake if you have previous FAA experience.