John Desmarais
Explorer
I played a fair amount fo D&D way back when using the Rules Cyclopedia - which is kind of a single-book compilation of BECMI. To my mind, it was every bit as "advanced" as AD&D insofar as considering extra options to be advanced - but the options were different (many of which I liked better than AD&D). OSE/AF is much more along the lines of importing AD&D stuff in the B/X core of OSE. In some ways, I think I would have preferred an OSE w/ all the extras from CMI imported in (for example, I preferred BECMI & RC Weapon Mastery over AD&D Weapon Proficiencies).I am curious to persue it, I don't yet have the books... but this seems in line even with the old BECMI Companion and Master sets which added options akin to AD&D but didn't quite seem 'right.'
It would seem that the B/X/BECMI/OSE systems really shine with just the Basic/Expert level stuff without too many trimmings.
I think ultimately, if your preference is straight B/X, OSE/AF probably as very little to offer you. If someone is looking for an easier to read AD&D workalike, OSE/AF can be pretty pretty attractive. I'll end up using it myself. My typical group of D&D players prefers AD&D over B/X, and I don't care enough to be a curmudgeon about it.