Alex Koppelman in Salon has done a fine job of analyzing the reaction to this cover. I grow weary of the indignation, whether serious or false, about stuff like this. It's worth a chuckle, that's all.
And, as Koppelman says, it's a distraction from the important article on Obama in this issue:
"The cover of the New Yorker often has little to do with the articles inside it. In this case, though, there's a tangential relationship, as the magazine's Ryan Lizza has a really interesting profile of Obama, done by looking through the lens of his rise in Chicago. In fact, if I were Lizza, I'd be pretty upset at my editors today, as this controversy has ensured that his article is going ignored. Like so many articles in the magazine, it's long, complicated and detailed, and reporters and commentators who are discussing the cover are skipping over the article, presumably for reasons of time. (The reason I'm behind the curve on posting about this, in fact, is that I took the time to read Lizza's article.)
Even though I subscribe to the New Yorker I always read the important political articles online, because out here my magazines are often a month or more late. And this is an important article. I feel after reading it that I have a sufficient understanding of what Obama and his campaign are about.
More: Now here is some real political cartooning, as only Steve Bell of the Guardian can do it! I loved "Maggie's Farm," his series of strips about The Thatcher-Reagan romance and other matters.
Obama supporters need to stop being so namby-pamby. Or, as Truman famously put it, "If you can't stand the heat, stay out of the kitchen!"
(Click on pic for the full effect.)
More: This one's even funnier.

Yet more: This is no gentle Sparky. Tom Tomorrow would not be capable of anything so vicious! I'm all indignant, aren't you?
These are like mixed nuts. I can't stop with just a few.
But I'll stop here. It's time to go clean my house.
Oh, just one more, from 2003. I submit that any cartooning you see in the U.S. is pretty mild compared to this!
Now I'll go clean my house!
And even more: this famous 1871 classic, titled "Let us Prey," by Thomas Nast on Boss Tweed and his scandalous political machine, with their whole edifice about to crash down on them.
Even more! This is too rich. By Andy Borowitz. This ought to be the last word on the subject, but it's just so much fun to comment on. I am cackling away here.
I'm going to stop this and go swimming at Richardson Beach.