The movie was gawd-awful, but in a fun way. I left the theater not missing my 26 dollars.
Reeeaaally could have been better though. Like, even by "mindless action/adventure movie" levels, it could have been better. Ironically, the acting wasn't bad, and neither was the dialogue (sans Riddick's, way too much cheese). The characters were all pretty smart and entertaining for the most part, too. But my god, the story was all over the place, the fighting scenes were bland and uninspired, and the CGI creatures were disappointing.
Also, Riddick himself is reaching Gary Stu levels in this franchise. His fight against Bautista literally ended with an asspull.
And don't be fooled into thinking this is anything like Pitch Black. The monsters only become a focus of the movie in the last third of it, and unlike the creatures in Pitch Black, these things get mowed down effortlessly. They're not nearly as threatening or omnipresent as the things in Pitch Black.
I really liked Starbuck's character, but she suffered from being in a cast that was way too large.