Fahrenheit is also based on water's phase changes, but the 0-100 range just falls nicely around the range of common ambient temperatures. The basis in water is nice because it's abundant and thus makes calibration of a thermometer easy. My contention is merely that the specific values of the phase changes are not so important that it makes the Celsius scale inherently better. I like that the ambient temperatures outside fall nicely throughout the 0-100 range in Fahrenheit, and I think that is just as valid an argument as water being liquid within this range.

And perhaps I'm particularly swayed by this argument because I live in a place that has cold winters and hot summers, so I see the full range of 0 to 100 in the weather. I'm also not going to pretend that growing up using Fahrenheit is not the main reason for my continuing usage of it.

I just wanted to point out that I'm convinced by the arguments in favor of the metric system for everything except Celsius. For that one, I just don't think water is as compelling an argument as is always presented.