I think it rather depends on the problems you have to solve - but in plain and simple terms a lot of clever things you want to in the browser client have already been done for you in jQuery, possibly with a plug in.
The two example I have of making the complex trivial are:
1) I needed to show a message if changes had been made in any text box (you have changes to save), this took me minutes in jQuery - a very few minutes - from cold with no practical jQuery experience.
2) Autocomplete in an MVC app - add plug-in, add data, done for basic, add helper method in server side code, even more done with lots of ajaxy goodness.
You don't need helpers to do this, but in the above two cases I spend a small number of minutes adding debugged code to my app and immediately get the results I want and reasonable certainty that one lump of code won't tread on the toes of another.
Heck, document.ready is worth the price of admission almost all on its own.
Essentially the answer to the question is to first ask "how can I use scripting to make my web applications better" which leads to "how do I use jQuery to enable me to add the functionality that will make my web application better" which I think will take you where you want to go...