Mark me down as one of the people who had a bad experience with fitment of the Cold Case all-aluminum G8 radiators. I could've lived with that, but after less than 3 years installed (and not driven that often) it also started leaking. I was about to give up and shell out for the ACDelco OEM unit (which has plastic end tanks but at least a limited lifetime warranty), but then I noticed a Mishimoto all-aluminum radiator listed on G8Only. Listed as a direct fit for VE Commodores, but specifically not tested on 2009.5 G8s or GXPs. I have an '08 GT.
And the same item listed on the Mishimoto site:

I don't know much about Mishimoto, but unlike Cold Case I'd at least heard of them before. Has anyone tried one of these radiators in a G8?