There's a plot in there, to be sure, concerning itself mostly with interdepartment squabbles and the location of the drugs sought by the police, but the movie is really about the action.
While hardly an accurate portrayal of police tactics, First Option does have several things going for it: (a) there's lots of troops in most of the scenes (most of the action is done by fireteam) and (b) these troops all have automatic weapons. (which is realistic for the situation) The editing and sound production help drive home the violence of these conflicts, which are the meat and drink of the movie. There's a few explosions to help liven up the gunbattles, giving the whole film a nice balance of action.
First Option is far more motivated towards pseudorealism than most action films. The police have to work together to win, rather than relying upon a maverick cop who can slaughter the badguys while the rest of the police force looks on. The team is the important thing here and that really does come through.
The cinematography works well for the most part - most of the action is filmed outdoors during the day and is consequently easy to follow. There are a few too many closeups at times, but not enough to rob the action of its impact or value. Sound production on the firearms is clean and much better than the average Hong Kong film (no stock popping sounds here).
Check it out if you want a movie about fireteam to fireteam conflict. If that doesn't grab your attention, then give it a miss.