Are pets good prep for parenthood?

 I saw this blog on Today's Parent where a pregnant lady raises the question of whether or not puppies can prepare a couple for a baby. This is something I heard more than a few times prior to having kids: "Get a pet (usually a dog) as practice for when the baby comes." 

As the Today's Parent blogger points out there are parallels: the inability to communicate, the need for attention, sleep deprivation, and of course cleaning up the poop. And there are obvious differences as well that need not be mentioned.

In the end, is it worth it to "practice" being a parent by getting a pet, or is it best to just enjoy the freedom (and sleep) while you have it?