I cannot confirm the comments mad before because it's search is powerful, and now with Spotlight support it's even better.
Take a look at the tutorial video's on their site and you will learn a lot you didn't know before.
I tried many others but Devonthink Pro Office can even find word that are misspelled, in fact I m always able to find back wath I m looking for, and now from the Spotlight bar.
Also when there is a bug and I report it, they mostly fix it within a week.