How bad is it? It's half terrible.
Should you see it? If you like giant monster movies... okay.
The first half of this film is slow, full of enormous plot holes, has poorly done humor (most involving a security guard) and is just a waste of time, with one-dimensional characters spouting pointless lines of dialog. Once it starts going in the second half, though, it's fun to watch. A giant serpent and its army seeks two reincarnated lovers needed to ensure its immortality. When the serpent attacks L.A., the CGI assault is quite good. Supposedly, this was a hit in Korea, where there's a legend from which this seems to borrow its plot.