I've got a side charger from Fulton Armory, similar to the white oak I guess. Bought it and a barrel and had a local guy build the upper from parts.
You still retain the use of the normal charging handle, which is good, because the side-charger is only held into the bolt carrier by a few screw threads, and it does tend to come loose if you don't check it frequently. I've seen where people would replace it with a plug, but I agree with White Oak.. keep the normal charging handle too.
You do loose the shell deflector and dust cover, if that matters to you (or the guy immediately behind you to your right). Having the handle does help in a few specific circumstances, and its great for shooting 3-position in highpower competition, but I could see how left-side may be a more optimal configuration on a defense carbine. You can also use it as a slide release too.