Well, there have been many articles on the WWW which would suffice “Why jQuery is the choice”. To me, it’s just precise, well structured, high learning curve and easy to use. When I was in the beginning of my Undergrad back in 1999, there was no library to deal with the cross browser issues (Netscape used to make life miserable for javascript programmers). So we had to write longer scripts for a specific purpose and handle the cross browser issues. Thomas Brattli at dhtmlcentral gave some pretty good scripts on menus and some libraries which we used to implement. But above all there was no such good library which could do magics, a library that you can extend easily the way you want, something meets the real programming standard. The journey to making javascript framework began much early. There are quite a number of libraries that started namely mochikit, prototype, mootools, dojo etc. But you should use jQuery for :

1. Very Lightweight, weighs less than 20k when minimized and gzipped.
2. High learning curve.
3. Super chainability. Almost Every jQuery method returns the Jquery object which lets you put methods in tails one after another. like $(“#div_one”).css(“border”,”1px solid #000″).fadeTo(300,0.5).slideUp(300);
4. Can be used with other libraries such as mootools using noconflict().
5. Easy to write plugins.
6. Code becomes short, sweet and easy to understand.
7. You don’t have to be a Javascript geek top write jQuery codes.
8. IMPORTANT :  Vast community support and contributions.
9. Used by major open source applications like Drupal, Wordpress.
10. Microsoft chose jQuery to use it with their applications. (may be a good point to some MS fans )
11. Very easy to play with DOM. Lot of built in methods integrated. DOM selectors are very untuitive.
12. Supports XPATH selectors.
13. VERY VERY easy built-in AJAX utilities. (leave me an email if anyone needs to know how easy this is).

Ok.. enough for now. The list could go quite long.

More to come soon.