Minor correction: The maximum time an appointed senator could sit is slightly more than 2 years, depending on the state, not 6 years. If the state doesn't hold a special election after a senator leaves office (which it totally can by the 17th Amendment), it *must* hold that election in the next general, that is, two years later. So if a senator were to die a month before election day such that another election couldn't be arranged in time, and the state didn't hold a special election, the appointee would sit for 2 and a half years until the next general.
This is part of the reason why Hillary Clinton's senate seat isn't overly attractive to serious Republican challengers (of which there is only one in New York, Giuliani, maybe.). She was reelected in 2006, so there'll be a special election in 2010, and then the normal election for the seat in 2012. Part of the reason people take Senate races seriously is that if you win it, it's yours for six years, but it'd be a mere 2-year hold for a theoretical Republican victory. Then it'd have to be immediately fought over again in an election year, and election years increase turnout. In a very Democratic state like New York, that means more low-information voters who just vote a straight ticket, so presidential election years tend to be bad news for downticket candidates in states not a close match ideologically. (That is, it's bad for Republicans in blue states and bad for Democrats in red states, moreso than in off-years.)
Anyway, special elections are notoriously bad at picking good candidates thanks to the low turnout, and furthermore they cost money. I say just let an appointee take the slot, but have some kind of commonsense rule that can forbid charades like the Roland Burris show - maybe some kind of "the legislature can veto any appointment the governor makes, but only with a 2/3 majority, and furthermore lack of legislative action within 14 days = appointment goes through." Man, what the hell. All I can say is that Burris better get primaried out - the Democrats will probably lose with a desperate mediocrity like him on top of the ticket. I think Carol Mosley-Braun managed to do that in 1998 in Illinois after her corrupt and ineffective time in the Senate. Which was a shame, since she was the first black female senator, but nevertheless an awful one.
On the other hand, I'm not a fan of too much concentration of power, and blue state moderate Republicans are probably healthy for the Republicans as a whole. So maybe if the Illinois Democrats lose in 2010 it won't be so bad after all.
