I came across Delineato Pro almost by chance while browsing the App Store. A quick googling around, after reading the developer interaction with his users on macrumors forum, I bought it just to try it out. I wrote the review with it as you can see below. For the search engine: I recommend giving a try, especially if you are frustrated with the complicated feature set of OmniGraffle, and find pure mind mapping tools too restrictive in terms of layout.