Okay, so Luke sees his friends are in trouble in a "City in the Clouds", pisses off Yoda and OB1 by quitting his training and flies off to save them.
Before he can save them, he gets into a duel with Darth Vader, learning this was all an elaborate trap for Luke. Meanwhile, Leia, Lando, Chewy and C3PO make their own escape and only got in trouble when they had to turn around to go back for Luke.
So how did Luke's presence on Bespin make any difference in his friends' escape?
Once R2D2 is split off from Luke he does several things that completely change the outcome of Leia and her crew's escape-
1. He kicks up a smoke screen to cover them from stormtrooper fire.
2. He accesses the city computer to crack the lock to the MF's landing platform. Lando couldn't even crack the password.
3. And finally, R2 activates the hyperdrive in the MF, allowing everybody to escape the Empire.
None of these things would've happened if R2 wasn't there. Oh yeah he finished fixing 3PO also. But that's neither here nor there.
Like most forum posts, I was hoping for a discussion about the question. I thought it was a valid debatable subject. When no such discussion occurred, I noted the answer in my opinion and figured the thread would drop off.
Ironically, now the format of the post has drawn more reaction than the original question. Oh well...