It all seems to be a bandaid fix to me. If your cooling system is working properly, there shouldn't be a need for additives. Now, I understand running trails in AZ in July with the A/C on places a ton of stress on the cooling system, and in that case it may be worth it. If you are having issues with your rig running hot on the street, I'd delve into the real problem first.
In my experience slinging parts at Advance, the people that buy Water Wetter, etc are the same people that buy head gasket repair in a bottle vs. fixing the dang HG.
My 01 runs right at 210 on the trail, with the aux. fan occasionally kicking on for 30 sec. or so. I'm adding hoodvents soon to augment cooling, but it works good enough for me.