It was actually very impressive in terms of semantic understanding, but the index was pretty awful. I either got exactly what I was looking for, or no hits at all. I can imagine that they'd get massive value by focusing on more information-rich natural language sources and de-prioritising images or structured/knowledge queries for the time being. Some good partnerships to provide instant answers a-la Duckduckgo's goodies would be excellent.
I also can't express how much better the Brave brand will be for them - even 'Tailcat' is a much better name. Cliqz sounds too much like an off-brand, gutter ad seller to ever have credibility, and I say that as someone who was fairly impressed with their tech.
I am worried that they're currently pitching this as a general purpose search engine at the moment when it will be a while before it can even pretend to compete with Google. I would advise for them to find a niche where they can whip Google into next week, and then expand on scope from there.