NYC, Venice and Paris seem Marmite places that people either love or hate. I love them all. Also have only positives to say about certain other unpopular destinations mentioned: Florence, Rome, Vienna, Pisa, Niagara Falls and the US state park, Dublin and its surrounding area. I also love Bergen, Tromso, Alesund, Stockholm, Istanbul, Maine and Arcadia State Park, Chesapeake Bay, Cape Cod, and Montreal.
Places that felt intimidating, dirty or otherwise unappealing for me include Miami, Kay Largo, Cairo, Alexandria, Naples, Thessaloniki. Agree about Brighton and Blackpool!