You can self host it which is cool and means that if the company's funds dry up and they stops development (hopefully never), you can continue using the product. With Google Code shut down and Github losing 66 million in 9 months in 2016, it's an important question to ask about where you keep your source code.
Featurewise, I haven't noticed anything that I can't use Gitlab for that I wanted to do. The interface is still less familiar to me than Github, but that seems to be a function of it being changed relatively often as well as the time spent looking at it.
I also like how much Gitlab embraces open source. They recently acquired Gitter and will open source it. Even though I mainly just use it as an alternative to the still more popular Github, I'm considering picking up one of the Enterprise plans to help ensure the development pace continues like this!