I've read a sci-fi story set on a cold planet where methane was fulfilling the role of water. There were methane rivers, seas, it was falling in rain, and it was the basis for all the chemistry.
It sounded reasonable, but I'm not good enough with science to know if it was legit.
One thing i overlooked earlier is water's propensity to form acids and bases, which support all sorts of useful biological functions. Methane's hydrogen atoms are tightly bound and methane itself is has no dipole moment- meaning it may have the same physical phases as water, but I am skeptical that it could fully support life as a substitute.
...not to mention that you also have to do away with an oxygen rich atmosphere as well...
It sounded reasonable, but I'm not good enough with science to know if it was legit.