I have mixed feelings about this. If it can make searching for existing posts a bit easier, I'm all for it. However, I think the old interface did a fine job.

If it were me, I'd have polished the modal popup a bit further, doing things like autofocusing on the search box and adding selective search (like searching only posts, pages, etc).

Maybe a bit of parsing like Google would be nice, such as typing type:page to narrow down results more easily.