Having coded in many languages, and recently when using MooTools instead of jQuery, i’ve come to realise that most actual programming is pretty language agnostic. What I mean is that most languages do the same thing, just very differently, but it is how you contruct your code that makes you a good programmer
Chances are, if you are good at jQuery you will be pretty good at MooTools (after learning the new declarations etc). The same goes for in a larger extent SQL/MySQL/Oracle or ASP/PHP/Ruby etc.
This stems from when I was at college and we would write psuedo-code, programming without any actually code. Something like this:
if number is greater than or equal to 10 then
write "congratulations, you are a winner!"
Now this very basic bit of programming isn’t very complex, but when building up larger bits of code, the skill comes in how you construct your code, not what language you write it in.
note: I am still a huge fan of jQuery, but MooTools does look pretty awesome as well. Perhaps I’ll write my own little comparison once I’ve used it a bit more.