I can't think of Mae in any way other than a nickname, and for some reason it really, really irks me when it's used as a full name. It also looks really awkward to me, with the a in front of the e, although May is too wordy. I also think it's not substantial enough, and way too cute. And slightly hickish. The fact that everyone on this board seems to think it's the cat's pajamas awakens rebellious instincts in me and makes me actually HATE it.
So. In case you were interested in a dissenting opinion.
Which you're probably not at this point. But I'd much rather meet a Margaret "Mae" than a Mae any day.