Nothing in the article surprises me or is at odds with most of what I've already learned about Barack Obama's background, nor does it distress me much.

Bobby Kennedy, whose assassination I believe robbed the US of a potentially great President, was called "ruthless" - and for good reason.   Bill Clinton, who for all his faults was a helluva lot better President than many others (including the highly overrated and under-criticized Ronald Reagan and, especially, the present occupant of the White House), was a calculating politician aiming at the Presidency ever since he was a young kid meeting JFK.   (The pity is that Clinton wasn't enough of a strategizer to prevent Gingrich's 1994 "Contract With America" backlash and wasn't calculating enough either to keep his fly zipped while interns were in the Oval Office or at least to destroy all evidence that he hadn't. Had Clinton been just that much more calculating as a politician, Dubya would not have had a chance to become President in 2000.)

I think these two paragraphs make the main points:

http://www.newyorker.com/reporting/2008/07/21/080721fa_fact_lizza?currentPage=15

"Like many politicians, Obama is paradoxical. He is by nature an incrementalist, yet he has laid out an ambitious first-term agenda (energy independence, universal health care, withdrawal from Iraq). He campaigns on reforming a broken political process, yet he has always played politics by the rules as they exist, not as he would like them to exist. He runs as an outsider, but he has succeeded by mastering the inside game. He is ideologically a man of the left, but at times he has been genuinely deferential to core philosophical insights of the right."

...

"Another transition from primary to general election is now under way for Obama, and it is causing him a similar set of problems, all of which stem from a realization among his supporters that superheroes don't become President; politicians do. Judging by the reaction to Obama's most recent decisions—his willingness to support legislation to modify the Foreign Intelligence Surveillance Act, his rightward shift on interpreting the Second Amendment, his decision to "refine" his Iraq policies—some voters will be crushed by this realization and others will be relieved. ... "