We have a little bit of everything. DH gets a cell through work and the kids don't have phones yet, so I'm the only one on my plan. I get a limited amount of data (4 GB?), but I've never gone over. The only time it's even been at all close is when we're on vacation and I'm taking and uploading a lot of photos, using Google Maps and the Internet a lot, etc.
My cell plan is through AT&T. I'm a klutz and drop my phone all the time, so I switched to AT&T because they're the only ones that have the Samsung Galaxy Active, which can stand up to my abuse. Our oldest will probably be getting a phone in the next year or so, so I'll need to start looking into family plans then. There are plenty of months when I use the talk time on my phone for 10 minutes or less, and he's going to be the same, so we'll definitely prioritize data.
We still have a landline. It's for a lot of reasons--we still need it for the kids, especially when our oldest is home alone. It's bundled with our internet service, and for a long time it wasn't much more to have both than just internet (I don't think that's true anymore, unfortunately). And then there's the real reason we'll probably never give up our landline--DH and I aren't really phone people, and we both hate the idea of people constantly calling the phones we carry all day. People who might need to reach us, like family, schools, work, and close friends, have both numbers. But we generally give out the landline only. So far so good--almost all our telemarketing and fundraising calls still go to the landline, which is much more easily ignored.