What rom are you using? I know I've seen it in developer options on every jellybean rom I've used. I really haven't used ICS. I've stuck with GB and JB.
Alright, I just remembered I have a co-worker with an Evo V stock ICS, so I checked.
I see GPU rendering option but not HW Overlays.
Not that this is super helpful but just confirming that the option simply isn't there in ICS...
And OB, fwiw, both of those options are in JB roms so I assume they are different. I don't really know what they do, but I assume since they appear as two different options, they must do something different. I've seen people mention turning them on/off but I've never had the need to mess with them.