I used Water Wetter once. Noticed no change so I'll never buy it again. Of course I've never really had a cooling problem either as my system works very well and I've never been in an overheat situation.

Certainly a dilution of more water/less antifreeze combo results in better heat dissipation, this is well documented. Antifreeze is poor at moving heat, the water is the portion of the formula that takes it away. So more water = better heat removal. Of course less antifreeze also = worse freeze protection, less corrosion inhibitors, etc...