I've only read half the thread, however, to address some issues...there is a specific isotope of mercury that is not toxic, the heat capacity of pure gallium is lower then that of water, by about 100 Kj/kgK therefore will not cool as efficiently as water however it will do the job well (78% as good as water, this is assuming pure gallium). However, because the vapor pressure is lower (posted by someone? read it somewhere on this thread, it implies a mixed substance) the melting point is lower therefore specific heat may actually be lower, or higher, depending on the composition of the mixture. For the enthusiast removing the liquid metal block and using water would most likely be better. The only advantage I see without knowing more about the metal's composition (other then the fact that gallium is part of the mixture) is silent cooling which will eventually become mainstream for silent pc's. Don’t flame me yet, I've still got the rest of the thread to read