[Boromir88]

Legate, you bring up good points about the Eagles not being at the battle (and let's remember they do show up at the Morannon ). However, I am going to disagree with you with this one:

I don't think the Nazgul did much. Apart from crying and demoralizing the Gondorians in the few days before the battle,

I think the Nazgul had a great effect during the Siege of Minas Tirith and Pelennor Fields. This was while Sauron's Army was already swarmed at the Gate:

...But soon there were few left in Minas Tirith who had the heart to stand up and defy the hosts of Mordor. For yet another weapon, swifter than hunger, the Lord of the Dark Tower had: dread and despair.
The Nazgul came again, and as their Dark Lord now grew and put forth his strength, so their voices, which uttered only his will and his malice, were filled with evil and horror. Ever they circled the City, like vultures that expect their fill of doomed men's flesh. Out of sight and shot they flew, and yet were ever present, and their deadly voices rent the air. More unbearable they became, not less, at each new cry. At length even the stout-hearted would fling themselves to the ground as the hidden menace passed over them, or they would stand, letting their weapons fall from nerveless hands while into their minds a blackness came, and they thought no more of war; but only of hiding and of crawling, and of death.~The Siege of Gondor

I don't think the Nazgul (and the fell beasts they road) were swooping around gobbling up Gondorian soldiers as the movies portrayed...as Tolkien compares them circling above the City ('out of sight and shot') to vultures; vultures being carrion fowl. However, they were always present and having an effect during the battle:

So it was that Gandalf took command of the last defense of the City of Gondor. Wherever he came men's hearts would lift again, and the winged shadows pass from memory...
And yet - when they [Gandalf and the Knights of Dol Amroth~me] had gone, the shadows closed on men again, and their hearts went cold, and the valour of Gondor withered into ash.~ibid

I think the Nazgul did have a great presense about them during the Siege of Gondor, but do agree that the Eagles could not have helped in that situation, at that time, due to the reasons you gave.