One of its biggest problems is that it seems to have completely stopped accepting most search modifiers (like double quotes, minus sign, etc) - I think the site-specific search still works, but that's all. I don't know if advanced search still exists either; if it does then it's been hidden. (The 'search tools' modifiers or whatever they're called kind of work, but not well enough to make up for not accepting other modifiers.)
Wouldn't be a problem if the same thing didn't seem to be affecting DDG as well and making it very difficult to search for very specific things.