I have heard a yippy little dog once at POR and it did not carry on for long. I have a serious-ish dog allergy and was concerned about my fav resort opening their doors quite this wide for the furred friends, but... so far it hasn't been an issue. Pet allergies are nowhere near as lethal as others but they can trigger anaphylaxis and to that end I have started travelling to WDW with my epipen where I was unlikely to take it before.
Despite my dire concerns, it's really been a non-issue so far.
My main concern is really what happens when mousekeeping accidentally lets one out or gets bit. But, cross that bridge whenever.