Have just completed Mod 1 with BGS and only tripped up on Met by a couple of percent, which was the one subject I was really worried about.
I think it really depends on the individual. I have found Met such a tricky one to get my head around but yet had no problems with G. Nav, M&B or Flight Planning. The only other subject I was a bit concerned about was Instruments, but in the end it turned out to be not as painful as I thought.
It's on with Mod 2 now so can't comment on the those yet. Only why did Bristol have to start it off with Hydraulics, eughhh!!!
MD2K