I think that Rails is hard to learn for several reasons:
* unless you've used it before, you have to learn Ruby too
* Rails is fast moving and has a lot of pieces
* the error messages can be cryptic and hard to decipher
I've been developing with Ruby and Rails for several years now and I still encounter cryptic error messages.
As a newbie I found it incredibly frustrating when Google did not bring up an immediate answer, it basically built a brick wall around me. I don't think this is Rails' fault per se, it's just the nature of the beast.