It seems like poor UX to me. It's a little ugly how line length isn't constrained and you're unable to do anything but type a query into the box. Special queries would require memorizing commands or just doing without.
I'd prefer a multi-column layout, 'cause you're right that long lines are hard to read.
I don't use that many special queries, except sometimes "site:", and frankly if I have to type (or paste) the entire domain anyway, "site:" is way less effort than switching to a different text field, even if it were one of the defaults.
I'd be OK having a "More Options" link or something for the rare case when I want to search for images by color or whatever.
Having said that, I'm aware this is very much a personal opinion. Google can design their site for the majority. I don't mind.
I kinda like the collapsable sidebar present in Google Maps. However, I rarely miss the extra space taken up by the current sidebar on the main search results page.
Well, except perhaps my query at the top so I can refine it if necessary.