The hotfix apparently works around the problem parsing jQuery and so you can get some Intellisense out of the box and with a wee bit of marking up the jQuery code you can now get some pretty useful Intellisense from jQuery in the JavaScript and ASP.NET Html editor. The problem is that jQuery is basically one big function and since it failed to parse - you got nothing. Previously working with jQuery got you - well, nothing because the the Intellisense parser didn't properly parse the jQuery source file and so failed to produce any Intellisense for anything in the jQuery library. Jeff's post talks about how you can make Visual Studio's JavaScript Intellisense work better with jQuery.
Jeff King, who's one of the program managers in the Web Tool Division and who focuses on the JavaScript editor, has posted about another byproduct of the Visual Studio hotfix I mentioned a few days ago.