The Fall of Sam Axe is one of those things which isn't necessary, and you begin to wonder why it was even made. Filling in Sam's backstory is a good idea, but it's not something we couldn't live without. From a plot standpoint with regard to the series as a whole, nothing would change even if the movie were not made. Maybe we'll see the characters reappear in a future season at most.
So if the backstory isn't all that impressive, what's left? As a standalone story, The Fall of Sam Axe is a by the books narrative of the hero leading a bunch of commoners to victory over guys with big guns before the US military swoops in to save the day. There are explosions, car chases, gun battles, comedy, and typical goodwill from Sam--all components of a Burn Notice. Basically, this is a regular episode of Burn Notice extended an hour, in a different location, and minus Michael, Fi, and Madeline.
From my perspective, whether one enjoys The Fall of Sam Axe depends on how much he/she cares about time. It's not crucial, but it has its fun parts spread across two hours, and isn't a complete waste of time. On the other hand, The Killing and the premiere of Game of Thrones are tonight, so there are also better ways to spend two hours.
Score: 8.2/10
