Pettigrew:
I have yet to vote as there is simply too many people at the moment to be looking at. Cho is definitely being looked at, as I can not see too many reasons for her defense to simply be 'I know what I am' unless she truly is Mafia or has a power role that could potentially put her in danger with the Mafia.
It is true that Neville may be a Mafia cop, as they have the power to investigate a person's role, rather than their alignment. If he he investigated Cho and found her to be a power role, he may be trying to get the town to lynch her, that way the Mafia are free to go after someone else. That would also help to justify her 'I know what I am' defense.
Myrtle may just be a bad player or something, but she could also be trying to draw attention from one of the Mafia's power roles. With Cho and Neville, there is a possibility that it would be either of them that she is trying to protect, in a matter of speaking. I'm assuming that it is not all that rare to sacrifice a lower ranking person to throw people off of the trail of the power roles.
With Ron, I'm not too certain what to think, really. He claims to be an Insane Doctor, and the insane part has been confirmed by Crabbe. It would be a decent cover, I suppose. That role could help the town a lot, but he has to be certain of who he is trying to 'protect'. Either way, using his night abilities is a risk. Should he choose someone other than Mafia, we may lose a potential power role. Should he choose to protect Mafia, he may actually succeed and then we would still have to deal with them later.
As of now, I continue to withhold my vote until I have valid reasoning and explanation as to a sure vote against someone.