This is quite interesting because when I posted the thread I had similar views to what most of you are saying.
I believe Faramir would have made it to Rivendell okay, because if anything he was a better woodsman than Boromir, who I believe was more of a commander/warrior.
I don't think the Ring would have corrupted him as much as it did Boromir either; certainly not enough for him to attack Frodo on Amon Hen as his brother did. What happens on Amon Hen is the crucial moment then...
Assuming the party are still together, rather than here, there and everywhere, chasing after Frodo, what would have happened?
1) They may have avoided the uruks all together (Unlikely)
2) They face the uruks together, and if so, could the party overcome them?
Unlike the film, where Aragorn and Legolas get stuck in too, from what I remember of the book, only Boromir engages the orcs here. Could a united party overcome the orcs, where Boromir alone had failed? If they couldn't, the hobbits would have been taken prisoner and the others would have either been slain in the battle or executed. Frodo would have used the Ring to escape, and Sam may have made it with him.
This scenario would have a similar result to the actual version, except Aragorn would not be able to summon the Dead Men of Dunharrow, and Minas Tirith would most likely fall.
Should the party, on the other hand somehow manage to defeat the orcs, I believe all surviving members would go with Frodo to Mordor where they would finish up captured.
As for Boromir, I don't believe he would have held Osgiliath for much longer than Faramir, but it would have been a more costly battle for both sides. If he managed to defend the ruins too well, his force would have been cut off because the army defending the crossing at Cair Andross would lose whatever. If Boromir fell in this battle, I don't think Denethor would have fallen into the same dispair caused by losing his son on some useless quest. Instead, I think he'd have led his troops valiantly, just as Theoden did the Rohirrim.
There again, whatever the outcomes of any hypothetical scenario, the good guys had more than their share of good luck in Tolkien's version, so given the same doses of good luck, but in different situations, I'm sure the end result would have been the same in the end.