I think you do have to register for an account. They're a pretty reputable company, so there's no harm in doing so. You just don't have to upgrade to the premium version if you don't want to.
I liked Lookout's feature that would take a picture with the front facing camera if someone failed to unlock 3 times in a row. It then sends you an email with that picture. But other than that, many of its main features tend to be a bit redundant compared to what Google already offers. Google will scan the apps on your phone for malware automatically if you turn on the Verify Apps option in Settings>Security. And Android Device Manager can also help you locate your lost phone, as well as send a Wipe Data command remotely.