The storyline sets itself up well at the beginning, telling us that a group of Marines (all with various medals/honours) have taken Alcatraz as their base, hijacked some chemical weaponary and are pointing them at San Francisco whilst demanding millions of dollars compensation for the families of soldiers that have died in combat.
It doesn't take the usual route of playing out the government as a hapless mob, clueless as to how approach things, and it doesn't play the marines out as your archetypal bad guys, you're made to at least understand, and perhaps sympathise with their cause.
However it manages to fall down relatively quickly, with a massively overblown and completely pointless (in terms of advancing the plot) car chase sequence, that probably increased the budget by millions. And instead of developing characters and intensifying the storyline, it feels as though a number of corners are cut to get to the end.
In summary, it starts off very much like a thriller/action film with a difference, and ends like most other action films.