While the side charging handle is good in theory, I think it is not as practical as the AR charging handle. I know, I know. Everyone right now is shaking their head and saying "WTF is ACRFan talking about." Let me clarify. As far as ergonomics are concerned for a firearm, it is virtually universally agreed upon that ambidextrous control features are the most desirable. I personally could care less as all firearms are initially geared towards righty's which is what I am. But in the quest for the ever perfect firearm, I think a left side only charging handle is not a great idea except that you can charge the weapon without breaking the cheek weld, etc. I think the ACR got it right with the side charging handle being forward of the action and up high as well as being ambidextrous. I think the ACR is the first real weapon that I can think of that is fully 100% ambidextrous out of the box. Not even the XCR is fully 100%.
So While I think the side charging handle on the AR is "kewl," I do not think is necessary and I still prefer the standard AR handle which is mostly ambidextrous with the right charging handle.
Just my $.02...