Considering

Obama's rather shady and undistinguished career as a state senator, Newsweek's writer shouldn't be boasting of that, either.

This is what the writer says:

During the years that Obama served in Springfield, 1997-2005, he was forced to wrestle with the minutiae of health-care policy, utility deregulation, transportation funding, school aid, and a host of other issues that are vitally important to America's coming years, but that U.S. senators are usually able to dispose of with a quick once-over. State legislators have to do this largely on their own, without ubiquitous staff guidance, because staffing is not lavish even in the more professional state capitols. They enter into day-to-day bargaining relationships over the details of legislation with colleagues of both parties; there is no one else to do it for them. At the end of the session, they are likely to know the strengths and quirks of nearly everyone who serves in their chamber.

Well, that may have been true for legislators in general, but Obama was known for being "present" for votes much of the time he was there. The only thing anybody remembers him for is his shady connections with Rezko and the like.