A colleague posted on Chminf-l asking about the American Chemical Society's Just Accepted Manuscripts program. Most of the immediate responses were to explain the program, which is not what she asked. Here's the site's description:
"Just Accepted" manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society is posting just accepted, unredacted manuscripts as a service to the research community in order to expedite the dissemination of scientific information as soon as possible after acceptance. "Just Accepted" manuscripts appear in full as PDF documents accompanied by an HTML abstract. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). The manuscripts posted on the "Just Accepted" Web site are not the final scientific version of record; the ASAP (As Soon As Publishable) article (which has been technically edited and formatted) represents the final scientific article of record. The "Just Accepted" manuscript is removed from the Web site upon publication of the ASAP article, and the ASAP article has the same DOI as the "Just Accepted" manuscript. The DOI remains constant to ensure that citations to "Just Accepted" manuscripts link to the final scientific article of record when it becomes available.
The FAQ explains that this is opt-in and these copies will be removed when the ASAP and final versions are live.
Chemistry is kind of a funny field when you talk about scholarly communication and sharing (see and read everything from Theresa Velden's dissertation research on this, in particular). Journals are dominated by ACS with RSC and the other scholarly publishers following. In some areas like synthetic chemistry, there's a real reluctance to even share at meetings, no desire to post pre-prints, and tight control over data access. In more computational and analytic areas, it's a little more relaxed.
Pre-print server efforts in chemistry have been mostly unsuccessful. For one thing, the journals will not take articles posted elsewhere first. Second, there's this big tension with priority (now moving to first to file maybe will change patent things but there's still recognition issues).
With all that, there are still efforts to require self-archiving broadly across fields and to have disciplinary pre-print servers. The big publishers who are rolling in dough from the subscriptions from all the ACS accredited programs do not want to see these archives and self-archiving succeed, even though it's been shown that it doesn't harm subscriptions in physics.
Anyway, as I said on the list, this is a pretty smart move by ACS. It solves the problem of getting the science out there sooner, but still with peer review, and on the hosted platform. This version disappears and the doi points you to the official version when available so they keep the traffic in house. I'm sure the embargoes go from official publication, too, so this is more time the publisher has to disseminate the content and get attention before government funders and institutional repositories can share it.
I think it will be accepted by chemists because it is from ACS and it is after peer review. We'll see, though, if there are any typos and whatnot that offend people.
Edit to add: Thurston Miller points to a few viewpoint papers in Journal of Physical Chemistry Letters on OA (the papers themselves are not OA).