I haven't had a landline since 2004 but I'm considering getting one again. The reason is that neither my AT&T iPhone nor Skype via my AT&T DSL works all that great from my apartment. But I'm also looking at replacing my DSL modem/router in case that is why the DSL doesn't work. (That's what AT&T thinks is going on.)
Yes, it does. Calling 911 from a cell phone connects you to a big regional call center that gets your location and transfers you to your local one, whereas calling 911 from a land line connects you to your local emergency call center immediately.
Also, calling 911 from a land line gives the dispatcher your address. Cell phones will send along your location if they can get it, but GPS doesn't work too well indoors, and tower-based location can be off by tens or hundreds of meters.
For people who don't have children (and even then…) and have a cell phone, I don't really see a good reason to still have a landline at this point.
I know that in France, for example, having a landline doesn't really cost you anything more than having the Internet, so most people have one. But $13 a month for nothing helps cutting that cord.