EF 70-200mm f/2.8L IS II USM vs. EF 70-200mm f/2.8L USM

The 70-200L IS USM lens is still available for approx. $1300. Is it worth the additional $1000 to buy the 70-200L IS USM II?

Almost all of the reviews I've read state that the new lens is superior, but I've also read reviews suggesting that there is really nothing wrong with the older model.

I am an amateur shooting with a 7D. I want the faster lens for my kids indoor concerts which are very poorly lit. I'm usually shooting from the back of a school auditorium with a monopod and my 70-300 4.5 IS USM. The 70-300 is fine for outdoor sports in daylight. High ISO settings (2000-4000) and slow shutter speeds equal very grainy images.

Should I invest the extra money for the newer version of this lens?