Is no one from this community playing online?  This game is awesomely addictive in co-op (kind of sucks offline).
I already have 10 hours logged between two days, mostly on Johnathan and Alucard.  Alucard is amazing in that he can attack extremely quickly, and his swords are very powerful (the one handed ones anyway, his two handed swords are kinda slow).  Johnathan I use because I enjoy using him, although he's one of the only characters I know that I reach the 3rd stage boss from accross the screen with his knives.  No other character can seem to reliably get at that boss.  Oh, Johnathan's whip seems to increase in power as you level up his sub-weapons, of which I have about 6 or 7.