[Aiwendil]

Legolas wrote:

That quote points out that Gandalf was greater than Saruman, but observed him as leader of the Istari because the Valar designed it that way.

I'm not sure it's quite that clear-cut. The letter you quoted says that Gandalf was, in the event, the only one of the Istari that was fundamentally succesful in his mission. And it says that, at the time when he fought the Balrog, he was the only one who could lead the resistance against Sauron (which of course Saruman could not now do, simply because he had been corrupted).

This (and the whole plot of the book) suggest that Gandalf was morally stronger than Saruman, but give no clear indication that he was stronger than him in terms of power, knowledge, or anything else. I would say that in some ways Gandalf was superior but in others Saruman was.

This says Sauron was greater than Saruman. If Sauron is greater than Saruman and Gandalf is (at the least) equal to Sauron, he too is greater than Saruman.

Who says that Gandalf is greater than Sauron? The opposite seems to me to be far more likely. If we consider Gandalf and Sauron as individuals, then we must acknowledge that Gandalf was at this point incarnate and thus far less powerful than he was originally. Sauron was also incarnate at this point, but he had not willingly given up much of his power in the way that Gandalf had. He was still a Maia; Gandalf was a Maia in the form of a human. Sauron did not disseminate his power as Melkor did; rather he concentrated it in the Ring. But as long as the Ring existed, it seems that he retained most of the power he had put into it.

You do make a good point with the quote about Cirdan. I would say that Gandalf was wiser than Saruman and had greater strength of will and a greater ability to shape the counsels of Men and Elves. But I think that Saruman had greater skill and knowledge and possibly greater personal power. In the end, Gandalf's greater wisdom and willpower serve him better than Saruman's skill.

Iarhen wrote:

1. Tom Bombadil. Since we dont know his nature, we do know taht the Ring had no effect over him. I.e., he had control over the Ring's effects over him. But if he wanted to use it for his purposes, would he be able to? I think it would depend on what his nature is... a maiar?

I don't think he had 'control' over the Ring's effects over him. Rather the Ring had no control over him, in part (or in whole?) because he did not desire control over it. The question about what would happen if he tried to use the Ring for his purposes is, I think, moot; he simply would not do that. If he did, I expect that his attempt to control or use the Ring would allow him to be controlled by it, just like everyone else. The very reason that the Ring doesn't affect him is that he doesn't try to use it.