Lots of Egyptian tweets compared the speech to Anwar Sadat's address before the Israeli parliament in 1977. The prevailing attitude, though, appears to be "trust, but verify."  Younger twitterers in the Muslim world seem to be ecstatic. A lot of attention is being paid to his language ("Muslim communities" instead of "Muslim world."  Israelis seem to be upset; the settlers are irate.

Here are some reactions from my Tweeps:

@marcambinder We Israelis are going to be most interested in precise definition of 'continued Israeli settlements.' @ALKASOM

@marcambinder a call to obliterate our preconceived notions of what is possible in this world & an in credible tonic against cynicism @JEFFoAKLEY

@marcambinder Obama presses the re-set button; a sweeping speech aimed at bridging a deep chasm - but laid out no formal proposals or plans @WESTWINGREPORT

@marcambinder Obama showed himself to be a true world leader. He is inclusive, and his observations of shortcomings always include ours too CSREAD61

@marcambinder Wide-ranging, and lacking much of anything that will change anyone's mind one way or the other. No apologies, very evenhanded. @WSLACK

@marcambinder Excellent speech, and though I'm an Obama skeptic, I'm impressed by how Osama bin laden deemed Obama's speech a threat. @STINSON

@marcambinder Most exciting part of speech was reaction to govt transparency and will of the people. That's BIG w/ Muslim youth in Egypt. @GANESHPURI89

Here are other reactions, as compiled from the #cairospeech stream.

@queenrania (yes, that Queen Rania!) "An end to the Us-Them attitude? ... Obama's words: genuine & thoughtful. A much-needed change in tone re: east-west"

Elizrael: Likud MK Danon:"Obama signed a pact w/ the Arab world &gave a prize 2 Arab aggression, which has been going on 4 over 60 years"

BreakingNewsAP: Israeli settler spokeswoman says Obama's speech in Cairo was naive and out of touch with reality.

yacketeeyakking: RT @alexlobov: @sanasaleem ah well, when all is said and done, what else is there left to say but insha'allah?

kshaheen: It's funny watching the more pessimistic Arab commentators on TV get a lot of pushback after the speech

salmansqadeerRT @Elizrael: Israeli r-wing politicians attacked the #CairoSpeech, claimed it was "dangerous", exhibited "appeasement" & adopted Arab POV

alexlobov: @sanasaleem ah well, when all is said and done, what else is there left to say but insha'allah?