- autocomplete of e-mail addresses
- collapsing/expanding nested e-mail conversations
- search suggestions
- navigating your inbox while simultaneously composing a new e-mail
Actually, I agree with both sides of a debate here: progressive enhancement is a really great idea and moreover it's completely insane to require JS and lots of potentially buggy and maybe even harmful JS libraries just to see what the page is about. On the other hand, non-JS and JS-based designs and implementations are just too different to be developed together - I know, I tried, multiple times - and what you really get is a blatant violation of DRY principle and twice as high cost.
In short, until we have a set of non-JS components (HTML5 new input types are an example), which are common and make it possible to translate JS-based design to non-JS one without whole page redesign, we're going to see people over-relying on JS and not providing alternatives. Which sucks.
A lot of others keep telling me "but you're missing out on tons of cool stuff", to which I reply "most of what JS is used for, I do not find 'cool'."