We're better than the 90s! The cutting-edge-features-that-only-work-in-some-browsers today aren't proprietary (à la ActiveX) and will eventually make it into every browser.

I read an article a while back (anyone have a link?) that argued that "best viewed with" helped push browsers and the web forward tremendously. IE 9 is evidence that it's happening again.

HTML5 could really use feature publication — if authors could easily detect support for next-generation features (`if(!document.support.canvas){ tellUserAboutNewBrowsers(); }`), they might be less likely to lock out browsers by name.