DEVONthink and DEVONthink To Go can be comfortably used with OmniFocus by using item links. Many other applications support URLs, too, and can so link back to documents stored in DEVONthink. For example Things from Cultured Code which works with DEVONthink very similar to OmniFocus:
As a couple of the commenters to the linked story point out, you can use the Things quick entry hotkey on your Mac from within DEVONthink (assuming you’ve set up the Things helper app) to automatically create a task in Things with a link back to the item in DEVONthink. Setting up your task in this manner will create a link that works on both Mac and iOS. On iOS, you can use the share sheet from within DEVONthink To Go, and get a task with a link back to the item in DEVONthink.
This is important, because Things doesn’t support attachments. Since DEVONthink links work cross-platform, DEVONthink is a great candidate to use as your Things file system.
Why go to this trouble, instead of using an app like OmniFocus, which does support attachments? After a few years of using Omnifocus, I’ve been putting Things 3 through its paces. It doesn’t have quite the power and flexibility of OmniFocus, but I’ve been surprised to find it actually might fit my workflow better. I have many, many one-off tasks, as opposed to projects, and Things seems better suited to that. The visual representation of Today and Upcoming, as seen in Things, can be done in OmniFocus with some customization, but the visual representation of this in Things works with my brain a bit better.
As David Sparks, aka MacSparky, has mentioned, there is value to using a tool that gives “delight.” Right now, I’m finding that Things gives me delight in ways that OmniFocus doesn’t. It keeps me working toward getting my tasks done. We’ll see if that lasts after the newness of the app wears off.