Really good watch, will probably watch again, and can recommend.
Look, it's a movie based on a video game about shooting demons from hell. It is far from perfect, it's probably a horrible Doom movie, but apart from that, this is a lot of fun.
It follows most of the zombie rules for infection, but the learning curve is one of the things that keeps the movie interesting as it drip feeds information as the infection gets out of control.
As great as the cast is with this one, it seems pretty clear from the beginning that the big billers, Dwayne Johnson and Karl Urban, are going to go head to head, whether it be against or back to back against monsters.
The monsters are done with great practical effects, they're creepy looking, and competitive with the available technology. They're even used in creative ways.
When it comes down to it, the movie is fun, and a reliably good watch.