I’ve cosplayed Keiichi at three conventions: Otakon, Anime Expo, and our small, local con out in west Texas. My fiancee went as Mion with me for Otakon and the local one (but didn’t get to go to Anime Expo with me).
At Anime Expo, I got to meet with @epika and some other cosplayers from both Higurashi and Umineko (there were two other Keiichis), and we also met Ryukishi07 there. He signed autographs, participated in panels, and it was a lot of fun. He was really charismatic and engaging even though he was speaking entirely in Japanese, and he was really amazed that I had the Vita version of Higurashi with me for him to sign. Some drunk guy mistook me for Shinji from Evangelion and refused to believe that I was a different character even when his friends backed me up, which was pretty hilarious.
At Otakon, we were stopped for pictures occasionally. There weren’t a lot of other Higurashi cosplayers, though we did follow another Mion down the hallway for a bit trying to get her attention so we could take her picture.
At our local con, exactly one person recognized us but was very thrilled to see us. He was really knowledgeable about the series, too, and even playfully inspected my bat to make sure I had written Satoshi’s name on it (I had). It was a lot of fun even though nobody really stopped us or took pictures.