This is a very interesting subject.
Personally, I use BibDesk as a bibliography manager. It has a lot of very handy features, as autofile, search into Skim annotations, etc. Papers is also very cool. But in my opinion, it has the drawback of being too centered into the scientific papers workflow (very interesting in ‘hard’ sciences) but not very useful sometimes in social sciences and humanities (we still work with books, non indexed articles and stuff).
The workflow solution that I recommend is the following : Use Bibdesk or Papers for your papers library. They are specialized solutions to the problem of organizing and dealing with scientific papers. You will never have the same features in DEVONThink (DT).
What DT can do is index your papers library folder(Bibdesk or Papers). I use DT to find relationships (thanks to its AI) between papers. You don’t need the fields of your database because what DT does is to find content relationships. It is very useful. With Bibdesk, what I do is to export my papers database as RTF (using a custom and beautified –I’m a visual designer also– RTF export template) and keep it updated into DT. That will help DT to find relationships between things.
What is cool in DT is that you don’t really need to replicate the structure of your bibliographic database, you just need to have the content indexed in a appropriate semantic manner. Generally Bibdesk or Papers allow you to store your papers in the Finder in a semantic manner. So you index that library and then you could use replicates to “think” into outlines or projects (even if for me, replicating is a pain because that horrendous red color of replicates in DT hurt my eyes. I think it is the bigger UI error into the big list of UI errors and oddities of DT).
By far, the workflow works very well from Bibdesk/Papers to DT. One thing missing (we still wait for DT2) is a way to do the contrary: let Bibdesk or Papers have links to your DT documents or notes. This could be done by simply having an URL for each item of your DT database (applications that have this feature : Yojimbo, Journler, Together, Omnifocus, Mail.app, Papers, etc.). Unfortunately, DT isn’t yet a very good citizen into the Mac OSX 2008 city of applications.
As for the writing part of the workflow, I recommend using Scrivener. Apart its already known features, Scrivener supports “multimarkdown”. Multimarkdown is an extension of the already known markdown format, but it will let you write LaTEX using a more intuitive markdown. So, if you have a Bibtex bibliography, you could always integrate it with Scrivener. This is a very nice feature.
I hope this will help you.