Just curious what is so nice / difficult about Haskell?
In fact, there are a lot of assumptions that Haskell throws out that you may be used to. One example is strictness. When you call a function in most programming languages, you can assume that the arguments to the function are evaluated before the function is called, but that's not necessarily true in Haskell. In fact, nothing is evaluated until its result is needed for something else -- such as adding two numbers; if you need to evaluate + (an addition), then you need to know what the values of the left and right hand sides are.
However, there are advantages to such assumption-breaking ideas. For example, you can have a function which produces an infinite data structure, and another function which consumes pieces of it at a later time. The functions need not know about each other at all. Such a system would be much more difficult to implement without this intrinsic laziness feature.
There's a lot more to learn, much of it quite mind-bending. If you grok Haskell, you won't design programs in other languages in quite the same way, because you realize what silly assumptions were being made before.