No question about it, he isn't a good guy. That man is insane....
Itachi--> "Your eyes belong to me now. I'll take them slowly...i want to savor this."
More importantly, i was wrong. Susanoo is completely invincible, and with Itachi's death, invincible it will remain.
Akatsuki members know that Zetsu's their scout.
Thus, Itachi would know that there was a chance that Zetsu was watching. Thus, if he really WAS a good guy, of-freakin'-course he would say things that came off as evil/despicable/indicative of a power-trip.
My belief in this is even FURTHER cemented by the fact that Itachi WHISPERS something, quite possibly addressed to Sasuke. WHISPERS!
Why whisper? Why mumble?
2 possibilities:
1. You're having trouble speaking.
2. You want to divulge information only to its intended recipient.
In other words, if the incoherent mumbling WAS a whisper to Sasuke, then it's quite plausible that Itachi whispered to keep Zetsu from overhearing and running back to Madara/Pein with the info.
I'm sorry, but there's too many coincidences regarding Itachi. First: he openly declares his desire to surpass Madara, knowing full well that Zetsu might be within hearing range. Second: he spoke in private with both Naruto and Itachi (Naruto off-screen, Sasuke with this whisper). Third: he winds up poking his brother on the forehead, which Sasuke had always taken as a sign of love/care/whatever. Fourth: despite his number of encounters with Naruto, he's not once made a serious effort to abduct the boy, always seemingly in favor of putting it off (he even told Kisame that there was no rush, that it would be better to seal the Kyuubi last...stalling much?).
This seems like the classic "villain-turned-out-to-be-a-good-guy-from-the-get-go" set-up. There are simply too many factors involved to rule out the possibility. Kishimoto has left himself a LOT of room to decide which way he wants to take Itachi in terms of moral standing (good vs. bad).