It's certainly more 'advanced' than any Lisp, including Clojure -- for the past few years (or decades now...), Haskell has been where new academic language research has been done. [1]
But that's just the problem. The fact is that Haskell is a research language standardized by a committee of academics without much experience or interest in real-world use. And it shows. Clojure, in contrast, is a language designed for practical purposes after years of experience from real-world use, mostly by one person, and while he's not as smart as the committee that designed Haskell, he has something committees rarely ever have. Taste.
In practice, I find Haskell beautiful. With Clojure I get things done.
[1] I'd be willing to say that today, if you are not fluent in Haskell, you are strictly not competent to design a new programming language. For the exact same reason you weren't competent to design new one without knowing Lisp from about the '80s through '00s -- unless you know Haskell, you are passing by most of the new inventions in programming languages done in past few decades simply because you have never heard of them, and don't even know you are missing them.
Furthermore, I'd probably disagree with the assertion that Haskell is more powerful once fully grasped. Lisp gives a lot of power to programmers (exhibit 1: the Lisp macro system). However, that means molding the definition of 'power' to suit my needs, and I don't really want to go there. I think that Haskell and Clojure are both very powerful and amazing languages. They are not mutually exclusive. I just happen to like Clojure more. Plenty of people go the other way. I, of course, still have a lot of respect and love for Haskell and hope to have time to do more with it in the near future.
As for why I switched in the first place, I guess it was mostly because Clojure looked like it would be so much fun. When you're young, what others perceive as weirdness can sometimes be exactly the thing that appeals to you. The reaction I had to parentheses is exactly the opposite of what experienced developers tend to have in the beginning. I loved them.
This strikes me as an odd "next step". I don't code in Haskell or clojure, but I've been eyeing both and the impression I got is that Haskell is harder to grasp but more powerful once fully grasped (and nearly as portable as C++). Sort of a superset of lisp. It seems that the next logical step after a couple of months of Haskell is more Haskell. It evidently worked out great for him, but I'd have liked to know why he switched to clojure.