Honestly, if you go see this movie for any other reason than to see 3D pyroclastics then you’re in for some disappointment.
I can’t tell you how bad the acting was because the dialog was so astoundingly bad. I think Carrie-Anne Moss and Jared Harris, both of whom are award winning actors, rolled their eyes at their own lines a few times. Kiefer Sutherland, who plays the bad guy, had cringe worthy lines, even for him. It’s that bad.
Case in point, the actor Jared Harris actually uses the word “bloody” a few times, as in “bloody Romans”. Hint, they didn’t talk like that. The shame is that Romans used lots of colorful metaphors. There’s an entire wikipedia page devoted to “latin profanity”. Translating that to English would have given the dialog some interesting quirks, oh well.