Martini-man,
No, I didn't have an ATP from elsewhere, but I had been flying for the military for about 10 years prior. I was studying the BGS notes a lot, but not quite full-time, except for the 3 weeks leading up to the exams (when the workload became quite unpleasant at times). I did all of the progress tests etc from the online course, then hammered the questionbank. Like Kash360, it does involve a great deal of work, but it's not insurmountable.
Cheers,
SBW