As you say, that the above three software are for different purposes, does it mean that even after one buys and uses Flashpaste, he must have to keep and use both flashnote and clipdiary also as you said those are for different purposes?
If you need it - yes. I actively use all three this utility.
I store a lot of notes in Flashnote: project notes, bugs, todo list, link that I should check and other information.
I use Flashpaste as repositary all texts that I often should to write: some code snippets, URL's for all my projects, there is a big folder for answer to letters with questions about my software etc. etc.
Clipdiary gives me feature of multy-clipboard. I can easy paste some information copied to clipboard 5 minutes ago.
So, I don't see how I can use only one utility for all this tasks.