Thanks. I'm glad it worked out. I'll look into the uninstalling (my package isn't supposed to delete the files, though) and figuring out a way to post more noticeable messages.

Though this add-on is a bit different from the tutorial. In fact, they're almost complementary.

What the tutorial does is speed up your site by only serving 2 concrete5-specific libraries if the user is logged in. If so, it also serves the local (non Google) jquery (why? I don't know.). If not logged in, it serves Google's jquery. (This is great is you don't have a site that expects users to be logged in most of the time -- otherwise it does nothing.)

My add-on doesn't care if people are logged in or not and doesn't change whether or not something is served. All it does it intercept the adding of a jquery (or jquery ui, or jquery ui css, or swfobject -- none of which the tutorial considers) file and rewrite that to serve google's version.

Two notes:
1. If you're like me and do a lot of development locally, on a laptop, with no internet, you wouldn't be able to use the method in the tutorial (at least not to test anonymous user pages) without going back in and changing the code (then remembering to change back). No internet, no google, no jquery loaded.

2. C5 has a cool feature in that it takes the header requests and makes them unique before writing out the headers. So if jquery.js is added in several places (the header element, plus a block you install next month), then c5 will only load jquery once. By changing the request just in the single element, it's possible that you'll end up loading jquery twice -- once from google and once locally. Definitely will make things slower, might even cause javascript problems.

So.... I definitely recommend you pay for the add-on. ;)