The plot is basically a mash up of most RE games up to now. You've got a mansion (RE1), arcade shooting, and OTT action (RE6). The story is ofcourse absurd and has quite a few plotholes, but you won't mind too much.
This movie isn't too scary, though I suppose RE hadn't focused on this aspect recently up until RE7 came out. There's really only one scene near the beginning that is horrific but even then I found myself laughing at the setup. This movie is more for fans of the RE6 action-horror setup.
The CGI ranges between bad and pretty okay. A few scenes look very PS3-ish in terms of quality, while others, especially a few of the action scenes, look adequate enough. Mostly the CGI probably won't bother you.
There isn't much music to speak of, but the English dub cast all do a solid job. I particularly liked Rebecca's voice actress.
Resident Evil: Vendetta is overall an entertaining way to spend two hours if you've played RE before. Anyone who hasn't won't get much out of this film.