I think one of the powerful features in Devonthink is links. If you have a big database and diligently make links this is superpowerful.
Is their anyway to visually view links, rather like the Brain or possibly tinderbox.
It is kind of applying a big data approach to your own data.
You mean something like this?
Well that would be a great idea and the above is a screen shot of a search result in DEVONagent Pro so it is cheating a bit! But I like your idea of viewing links diagrammatically like this and so I say +1 from me. Perhaps it could be a viewing option in See Also & Classify?