I have enabled this on my T2i. Supposed to extend latitude. How many of you are using it? Does anyone notice any artifacts or reasons not to use it?

I have it enable on my 7D and T2i. No reason not
to use it in my opinion, as long as you don't mind
having ISO 200 as your baseline.

Hmmmm... when I got the camera I instictively turned it on, but I then read somewhere it produced banding or something like that - in fact I was looking about the problem and found that the setting was the cause.

I'm not sure now though, all the camera settings where done only once for me. Did them and never looked back.

what it really does is just under expose the image little, maybe 1/2 - 1 stop.

the picture optimization OTH seems to play around with gamma. the latest firmware update addresses the camera making auto adjustments while in record.