my personal opinion about the commentaries and abhidhamma is they are unnessary for awakening(for some). i base this opinion on the fact that none of the arahants in the suttas studied the comentaries and as for the abhidhamma, the buddha (as far as i've understood) only taught it to sariputta and his students, meaning: it was not a teaching for the majority but rather for the select few (sariputta was the buddha's disciple formost in wisdom after all).
the buddha taught many things to many different people, there are of course "basic" threads running through all his teachings that bind them together, but there are different methods for different folks, a variety of meditation styles etc. what works for some wont work for everyone and not everyone is gonna even be able to follow the buddhist path (the buddha didnt convert everyone he met, and not everyone he did convert became an arahant).
now i'll dig around in the abhidhamma, and i've found some of it quite usefull, the rest i'll admit i'm just not understanding. i dont discredit it however and i'm not sure anyone who has studied it does, or would, i see it as a method of teaching, and of understanding, and i cant see anyone just writing it off as it's obviously helped quite a few people. (the only argument i've ever really even seen against the abhidhamma is a belief that the buddha didnt teach it, and as i dont know either way, i cant defend it on that basis, but if it is one's posistion that it didnt come from the buddha, then i would concede that for them there is no reason to study it)
the comentaries i have never studied, i've read bits and pieces here and there when teachers bring it up in notes or what not but thats about it. so again i am in no position to write them off either, i just dont have the time to find and read them, i am glad however that they are out there, so if for no other reason we have a historical record of buddhist thought.
for such an extreme liberal politically, i guess i'm a centrist when it comes to my dhamma