It's handy if you live in a place where the weather at home is significantly different than the weather where you spend a lot of time (Michigan and New York state have this due to the Great Lakes weather patterns).
When I'm sitting at work 20 miles south of my home, it's quite common for my home to be getting a major storm and my work to be bright and sunny. The differences can be more severe on further trips (going to visit my family 150 miles north or south).
With this I agree. While I think the point of "Windows Phone does things faster" is true for some sets of "faster", "faster" needs to be clearly defined as "not taking up your time" as opposed to actually running faster. "At a glance" might be the correct phrasing, the live tiles show you the information you need without needing to open the app.
That being said, I was merely replying to the OP's assertion that knowing the weather in two places at once isn't a good use case. It's no different than having clocks for two timezones.
When I'm sitting at work 20 miles south of my home, it's quite common for my home to be getting a major storm and my work to be bright and sunny. The differences can be more severe on further trips (going to visit my family 150 miles north or south).