jimbokun and dmaclay,
It really depends on the application. Remember, the client is always untrustworthy. You can trust them with their data, but nothing else. In three-legged cases, like an ad or some other third-party developed app hosted in your page, you can't even trust the client-side to have unlimited access to the client's data! Plus, there are remote script hacks that potentially will compromise the user's state or other information.
a catchy acronym for what all the cool kids are doing in the browser with Javascript
At Yahoo, we call it Progressive Layered Enhancement. Start with working markup and server-side logic, and then enhance it in layers to add functionality for the browsers that can handle it, so that it always works, even if a layer is missing or broken.
Having worked on a Microsoft stack in the past, I can say that it was nice to have a single language from end to end. It just really sucked that the language was VisualBasic. So, I get the excitement behind GWT and Pyjamas. Not that the author is wrong, I just think he doesn't really treat the material very well.