A recap of the Presidents we've had since 1952 (or, the advent of television):

Dwight Eisenhower: No experience in elected office.

JFK: Six years in the House, eight years in the Senate.  14 years in elected office.

LBJ: Twelve years in the House, twelve in the Senate.  Spent three years as Vice President before ascending to the Presidency.  27 years in elected office.

Nixon: Four years in the House, two years in the Senate, eight as Vice President.  14 years in elected office.

Ford: 24 years in the House before being appointed Vice President.

Carter: Four years in the Georgia Senate, four years as governor.

Reagan: Eight years as California governor.

Bush 41: Four years in the House, eight as Vice President.

Clinton: Two years as Arkansas Attorney General, 12 years as governor.

Bush 43: Six years as Texas governor.

So, Obama has more experience than four of our last ten Presidents.  If you don't count Nixon's and Bush's years as Vice President (when they were elected largely because of Eisenhower and Reagan, respectively), it's six of ten.  JFK and Clinton only had two more years of experience in office.  That leaves LBJ and Ford -- and both of them ascended to the Presidency through the death or resignation of the President.

Where's the complaint?  Obama is already a national figure, won an impressive victory in his first Senate election, and has the gravitas to be elected President.  What's more, many of the Republican contenders don't have a ton of experience in electoral politics, either.  Mitt Romney has spent four years as governor.  Giuliani was mayor for eight years.  Mike Huckabee has twelve years -- two as lieutenant governor, ten as governor.

Inexperience doesn't seem to be a likely charge against Obama -- at least, not one that will stick.  Not when the candidate running against him will likely be someone without much experience.