I liked Marcus initially, then went off him a bit when he mooned around after the lost cause that was Noirin. Tho even then, he could still pull out some great one liners. But you're spot on, since the wicked witch left, he's been superb, his diary room stuff is funnier than anyone else, and he seems to see what's really going on in the house better than most. I actually said to my other half last night, "I'd really quite like it if Marcus won", and I meant it!!
Definitely a member of THE irrepressible dark horse fan club