Astronomy is a bit unique in that there is no real hierarchy of journals in our field. There are really only four main "bread and butter" journals: Astronomica

Astronomy is a bit unique in that there is no real hierarchy of journals in our field. There are really only four main "bread and butter" journals: Astronomical Journal, Astrophyiscal Journal, Monthly Notices of the Royal Astronomical Society, and Astronomy & Astrophysics. A paper published in any one of these journals has roughly equal weight and "impact". I think this unique status will help OJA succeed - astronomers are already used to judging papers from all four journals with roughly equal weight. If some senior people get behind it and start making big, important papers available via OJA, I think it really might take off. Page charges can be seriously expensive. I think many academics would be happy to avoid the whole mess and just post to the arxiv and get peer review via OJA. It's already more or less standard practice to post to the arxiv either upon submission or acceptance, this just formalizes that practice and adds an element of certification of the result.