I can definitely hear some Jimmy Sullivan in there. I don't know if it's because The Rev is dead and isn't actually playing on that track and I have some psychological conflict with it, if it's that I just don't care for that song too much, or if I can really hear a difference between Portnoy's playing and Sullivan's, but it isn't quite right for me. When I hear the whole album I'll make my ultimate decision, but right now Portnoy is only doing what anybody could, and he hasn't come anywhere close to replacing The Rev. I think he might have the potential for it, but it probably is impossible so it doesn't matter.
(relatively) recent deaths in music:
Jim Chapin
Les Paul
Jimmy "The Rev" Sullivan
Ronnie James Dio
Paul Gray (Slipknot, a few days ago)
All major losses except the last one. Slipknot is pretty much dead anyway
Anyway, I don't think Portnoy has brought what is needed quite yet. He has brought something, but to me it's an undesired change... maybe I'm just picky.