Well, we are Facebook friends so you already know I have two last names, and so does my husband. :) We took each other's names, no hyphen. This makes for a really long double-barreled last name, kind of like Elizabeth Barrett Browning or Hillary Rodham Clinton or Ralph Vaughan Williams or a hundred other famous people with two last names I can't think of right now. :)
Honestly, it was a compromise. DH wanted us to share a last name, and I wanted to keep my name, so we both added each other's. It's long and kind of annoying on occasion, but overall, I think we're pleased with our choice. He offered to just take my last name, but I have an uncle with that same name who used to live in the same city as us, so I thought that would be confusing.
We don't plan to have kids, but if something changed, they'd get both last names, as well. I'd suggest for your kids that they get one of the last names as a middle name, or just give them both last names. They can decide to do whatever they want to with their name when they get old enough to legally change it or get married themselves.
Edited to add: I just saw some of the other discussion on this thread. To add a bit more info., my DH's parents never married, so he has his mother's last name, and now I have his mother's last name, as well. And since we still live in the city where we both grew up, having both last names makes for interesting and potentially helpful name recognition. Both families are well-regarded in the area for various excellent reasons, so being identified as part of those families is good for us (it's not like we're the Rockefeller Kennedys or something, but kind of along those lines).
The only bummer about us both changing names is that we had to pay for two new driver's licenses, two new passports, etc.