Foundation uses <br />s with its form fields (eg. <input><br />, etc), which just makes it annoying to style if you want to style anything ever so slightly out of the box Zurb puts you in.
I went back and checked; it was actually the lack of any wrapping container that was bothering me; <label><input><label><input> etc.
(Unless you're very careful with the styling it gets to be a pain in the bum to include non-standard chunks of markup underneath some elements, particularly if you want to arrange the label on the left and everything else on the right.)