While watching them perform I wasn't blown away by their sound but it was good. What was terribly disappointing was their look. The picture to the right doesn't do justice to their look on SNL, but it was as if each member of the band was a terrible parody of what they considered to be rock. The lead singer had some ridiculous wide suspenders, the bassist had an awful Elvis-type hair, the drummer had long hair a la Dave Grohl circa 1992, and the lead guitarist had a leather jacket under which he was flashing some stunning white chest. I cannot imagine being able to watch a live show of KoL and not feel a sense of lacking.
That being said, there are plenty of bands that I enjoy that I would rather have not seen them in person. My primary example is Jimmy Eat World. There's little that is visually appealing about that band, but they make such catchy music that I can't let them go.
On the opposite end of the spectrum there are artists whose looks perfectly fit their sound. Both Sufjan Stevens and Sam Beam (aka Iron and Wine) look exactly like I had imagined they would.
I realized immediately after writing the above paragraph that it's quite possible that I saw pictures of the artists before I had imagined their appearance so my judgment would be faulty. In order to be more honest, I conjured mental images of the looks of three bands: The Airborne Toxic Event, Ra Ra Riot, and Vampire Weekend to see if their images match their sounds. The verdict: they do, especially The Airborne Toxic Event.
On a different note, I would highly recommend all three of these bands.