On the topic of the actual apology, I thought it was fine. He should've done that instead of the funny half-apology he originally did, but honestly, I blame the Palins for turning it into what it has become. If not for them blustering over it all week, most people would've forgotten about the joke 10 minutes after hearing it. People who didn't watch the show would probably never have heard about it at all. The Palins daughter(s) might never have heard it or been embarassed by it, their friends might never have heard it or teased them about it, and we would all be talking about something else right now.
Instead, because of the Palins making a big deal over it in the media, everyone has heard the joke multiple times, probably the Palins daughter(s) more than most, and they're probably incredibly embarassed by it.
Btw, whoever said Letterman was afraid of getting fired...
And, I think, through all of this, we have failed to ask one very important question at the heart of this issue, which is... where is Alex Rodriguez' apology?! Stadium boy deserves one too!