I get that people have syntax preferences and that there's a certain level of "sniff" test that goes along with these things, but as a fan of programming languages I am always interested in the semantics. That is, I'm interested in what's different about this language and its combination of features and goals:
http://clean.cs.ru.nl/Language_features
> The uniqueness typing system of Clean makes it possible to develop efficient applications. In particular, it allows a refined control over the single-threaded use of objects which can influence the time and space behavior of programs. Uniqueness typing can also be used to incorporate destructive updates of objects within a pure functional framework. It allows destructive transformation of state information and enables efficient interfacing to the nonfunctional world (to C but also to I/O systems like X-Windows) offering direct access to file systems and operating systems.
When I read that I think, "Wow! That seems really neat and reminds me of linear types, and I should check this out". Maybe that's just me though.
It's also worth noting that the features page does not mention the word syntax. That's not a deep insight or strong evidence for anything really but it suggests that the designer was interested in the semantics too and that the syntax was a secondary concern.