Horrendously bad. I like Dark City and Knowing, also by Proyas, but this one is just terrible. No defending it. I like that Proyas goes for broke but almost nothing in this one worked. The only interesting scene was Geoffrey Rush as Ra, battling Apophis from his spaceship. Brenton Thwaites was bad, the love interest was bad, Jaime Lannister was bad, and Gerard Butler was, as almost always it seems, bad. Fight scenes were terrible and most special effects were terrible. This is the kind of movie where I was disappointed when Thwaites threw Horus' missing eyeball to him and Horus didn't just raise his eyepatch to allow it to land exactly in its socket.
But of all the bad things in this movie, Chadwick Boseman has to take the cake. Script and direction did him no favors but if you think Black Panther is going to be good you are very likely going to be very disappointed.
It did have Rufus Sewell, though. He should be in more movies.