The tentacles from the World Engine, yeah, they were kind of silly, but you know, that's half the fun of it, I think. 
Seeing Superman battle a giant robot onscreen at long last.
It makes zero sense for the World Engine not to have some defenses given its importance, and the tentacles were a pretty cool extension of the morphing Kryptonian tech we saw earlier in the film.
Add in the potential nod to Braniac in the tech/defense mechanism, and I can't complain about it too much. It feels a little bit out of place, but it should feel a bit jarring when it shows up, especially for Superman, who isn't expecting it.