Recently I discovered how to use javascript intellisense which helps a ton. You need to have SP1 of Visual Web Developer :
http://www.microsoft.com/downloads/details.aspx?FamilyId=7B0B0339-613A-46E6-AB4D-080D4D4A8C4E&displaylang=en
Once you have SP1, just add the following to the top of each JS file:
/// < reference path="lib/ext/adapter/ext/ext-base.js">
/// < reference path="lib/ext/ext-all-debug.js">
/// < reference path="myotherfile.js">
Not only do I get Ext intellisense, but also for objects from my own javascript files. Works great!
