jQuery is pretty awesome and doesn’t really enforce a coding style. Its coding model is instructional which is easy to learn and follow. It also has method chaining that I really like.
Other frameworks like Mootools and Prototype try to be modern by encouraging Object Oriented Programming style. So you’ll learn how to divide your code into classes, define methods, properties, inherit behavior and etc. If you like to be a serious software guy, you may enjoy such frameworks because OOP is their bread and butter. Their libraries are usually comprehensive and tend to be very nicely structured. I’d recommend them for larger projects though if I had the choice to use jQuery.
My final reason for encouraging you to learn Frameworks sooner than later is that once you get into one you’ll notice that a lot of your work is already done for you. Smart developers try to write as little lines of code as they could and don’t try to reinvent the wheel (I’m not suggesting to write a whole program on one line and be anal about optimization). You also want to to have less moving parts in your code because then less things could go wrong in your own code. Frameworks are really good for that particular reason.
The sooner anyone drops their preconceptions of the language, the easier it is to learn and use it.
Yeah. I have no idea what I’m talking about