"Unfortunately, Canon was probably placed in the worst lit area on the show floor, no art or great photos could be made with the new lenses, though I tried."
Which is why the 24 - 105mm IS L will continue to be the better lens when light levels are low with sharp images being possible as low as 1/6th sec.
I've never yet heard any client say images would be better if a sharper lens than the 24 - 105mm was used, so what's the point in a lens which weighs twice as much costs three times as much and has a reduced zoom range, and can't take decent photos when the light drops away?
Want a blurred background? Then use a prime! 2.8 is only just wide enough anyway.
The 24-105 IS L is an f4 lens
Who wants to deal with that in low light situations with moving subjects?
Get ready to crank up the ISO :\