I cringe because most sites on the web today are only liquid enough to stretch their design elements when they go wider but still typically have a fixed width (or marginally percent width) content area because incredibly long lines are difficult to read. The font sizes typically don't get bigger so you end up with either a slender column of content running down the center third of your screen or the page stretches so wide that entire paragraphs of text become a single, difficult to read line. NeoGAF itself is one such site that is so liquid that text becomes harder to read when viewed full screen.
Even with reactive design it's not perfect because simply making the font bigger to adjust for widescreen orientation just makes the user have to scroll through larger text or floating more elements into new columns also gets visually weird and can negatively effect the esthetics or ease of use of the site. Not all sites have so much content to warrant more than two columns.
Websites contain text and because text is easier read when lines are kept short websites work best in a portrait design orientation. Even a nicely designed 980px min-width liquid website typically ends up being a single column of content surrounded by huge empty space when viewed full screen on a monitor that can do 1920 or greater width. If all sites were reactive (which they're not) you'd still end up with larger fonts and multiple columns you might not have wanted.
I guess some of you are just used to seeing websites this way and it doesn't bother you but as a designer, that stuff bugs me. It's pointless to run your browser window so large if the overall esthetics (and in some cases readability and usability) suffer for it.
Like I said, most of the web isn't reactive. Also, not every design works with elements moving around. Often, you have a vision for what you want your design to be and making it reactive breaks that vision. For example, reactive design can work well when there are lots of content areas on a single page. You can start floating them and making more columns like I mentioned above. However, if there is only a small amount of content (say a single paragraph), then reactive design doesn't really solve the problem. I'm not trying to rag on reactive design (I think it's cool as hell) it's just that running your browser window crazy wide is eventually going to mess up the browsing experience. If portrait displays were the standard desktop display, the web would be better for it and running browsers full-screen wouldn't be an issue.
You should look for retina menu bar icon packs on macthemes and deviantart instead. Not sure how abundant those are atm, though.
