Funny, on a 15" rMBP it's too big.
In either case, there is no way to resize or move the window, the latter making referencing info underneath it annoyingly difficult. One has to either anticipating it happening, or find out, close the Spotlight window, move the reference window, then open Spotlight again.
IMO, a strong case of "what were they thinking?".
On a more positive note, the always-on quick view sometimes is handy sometimes even gives you more info than before. For instance, an application displays its version.