Just out of curiousity, how did this double negative come to be?
When I use it, it's often because I want to emphasise the fact that x is not y but is still similar in some way, whereas "like" doesn't necessarily stress the fact that two things aren't the same when stating their... likeness.
The ship's design was not unlike that of a Firefly class vessel, but it was a lot faster, like the Millenium Falcon.
Captain Reynolds was like Han Solo in a way. A great leader in times of need.
Yes, I'm a Firefly fan.