The hottest storylines at the moment as you have heard from me a couple times before is the Victoria/Trevor/Lydia/Brad/Phyllis quintangle, then there's the whole separate issue of Victoria's pregnancy. I'm also interested to see who the mystery man connected to Simone. The whole Ethan/Mia/Austin/Laurie/Jacob storyline has its moments.
I'll have to say the reckless Demetrius or the troubled Kip are the most interesting of the set. I haven't seen much of the other two to really develop a consensus on them.