[Keeper of Dol Guldur]

The eagles had been watching things all along; ever since rescuing Gandalf from Orthanc their role grew. It's clear that once that happened, Gwaihir was back and forth between his eyries, Radagast and Galadriel's houses in the least. He'd been in contact with her, probably often, because she sent him to collect Gandalf from Zirak-zigil; not Radagast. After that, we see eagles often scouting the three hunters. It's pretty clear they don't fly east of Anduin much as a rule of thumb, just like how the Nazgul don't yet fly west of it until 'their time has come'.

The eagles; aside from the Nazgul and regardless of the final battle, well it's not really prudent to fly near a volcano is it? That and obviously certain players like the Witch-King had some control over lightning, and Sauron had some sway with the East Wind . . . and pretty much had control over Mordor's weather. It seems likely Sauron would spot an eagle himself pretty quickly through the Palantiri, and be able to do something, even if it was too high for arrows. In his own land, Sauron had control of every aspect (well, except Frodo and Sam). The windlords couldn't 'simply' fly to Mount Doom until Sauron was good and dead. At that time, Gwaihir deemed it would be okay, and trusted Gandalf anyway.

Logic? When almost all hope is lost, what council is there in logic?

The Ring didn't corrupt Boromir - it played a game with his values, which it got the upper hand in for only a brief while. Don't villainize Boromir. Men of Gondor are the most honest, honorable men alive, and when he vowed to protect Frodo and to aid him in his quest, it was set in stone. Quite literally the Ring had to make a spell come over him to get anything done, so resolute was his will.

Good and evil in a traditional sense? Sauron was just a smart kid who got peer pressured into evil in the beginning because it made sense to want to set everything to orderliness. It was likely he, like Saruman later did, saw orcs as nothing more than a means to an end, and hated the filth, but thought it was necessary. In between Dark Lording, he was clearly a master artificer and spellshaper, and not just some 'evil archetypal tyrant'. There were certainly different levels of evil, expressed by the insouscient, destructive orcs, the confused and 'brain-washed' (I hesitate to use the term) easterlings and southrons, those who lust for their own gains like the Mouth of Sauron and Saruman, those who's lust was their downfall (Nazgul) and on a lesser note, the mercenaries like Wormtongue or the Corsairs who Sauron probably bought. I don't know if I'd say the Balrog was evil, it certainly hated Gandalf's type, all white-light and shiny and good. But it seemed more like a dissillusioned soldier, once of light, who doesn't buy into the Valar's crap anymore. Or at least, that's what Morgoth tricked it into thinking.

Why is the ring evil? Because Sauron put all his negative energy into it, not his positive. He kept his optimism and happy-go-lucky nature to himself, because the Ring was for creative purposes (note; destruction being a form of creation). The power it represents is considered evil, most likely because it is a power that demands utter dominance over all life, and that's usually looked down upon. Why is Sauron evil? Because he doesn't care how he achieves his final end. The end (the one he wants anyway) quite literally "crowns" the means.