Been on a persona kick over the last couple of weeks, finally finished P1, ran through P2 (PSP IS, and PSX EP) and and now on the final month of P3P (FeMC) and like most old school fans am saddened by the lack of Nanjo, Elly, Maya, and the rest of the EP cast. Baofu and Katsuya had one of the best antagonistic relationships I've seen in an RPG, and Maya is just plain win.
Still, I do like most of the newer characters in p3/4 with the horrible exception of Ken. I mean I disliked him on my first playthough of P3, but man I HATED him playing through as FeMC. He was awful, the fact that they decided that HE needed a romance route is still disturbing as all hell to me. The fact that in that route you sleep with him (in the Japanese version anyway) is just gross, and really makes me question just what the hell they were thinking.
As for the other majorly hated character in this thread Junpei, he was alright on my first playthough, but I actually loved the guy on the FeMC route, FeMC/Junpei may be my favorite bromance in the entire series.