No its not 'harder' to learn. You just have to understand the concept of applicative evaluation and prefix notation. Then recursion and higher-order functions. That is four things. (Macros can be considered advanced). In the end, all functions evaluates to a value. Thus functions are considered to be data. This value (data) is then passed on to the next function as arguments, and so on.. Anonymous functions is also something which kicks ass, and you miss such features when programming in C. This is one reason why C programs should be left as simple as possible, with as little abstraction as possible. (Fortran? Come on!)

>Lisp goes significantly farther towards shoving FP down your throat than Python does any individual paradigm.

This is simply not the case. It has the best OO system in existence. It has the loop macro (mini language). In actual practice I think lispers tend to not program so functionally because they're instinctively afraid of consing.