I use DevonThink as well and love it... but I also don't need to sync between multiple devices. All of my dissertation sources, notes, files, etc are in DevonThink - love the tagging and search features, folder levels, etc. I'm able to quickly find, navigate, and even discover relations I didn't discover before. Also, multiple file types and I now have the PDF -> OCR stuff for older documents. I keep my footnotes/endnotes/bibliographic info in Zotero.