If you like watching Jason Statham alternately kicking ass and skulking about, making the most of his three expressions (pissed off, smirking, and the rare laughing), and if you bring to each Statham film the requisite dump-truck-sized load of suspension of disbelief, then you will enjoy this movie. I did. It wasn't up to the best of the Statham films, which for my money would be the first Transporter, but it was fun.
I do have to warn you that Ben Foster, who plays his protege, is a walking heap of annoying suck. With each passing moment that he was on the screen, I found myself wishing ever more fervently that Statham would kill him.
As you can tell, The Mechanic is not a good movie, but it is a decent bad movie. If you enter it with the right expectations, you can have a very good time watching it.
The movie does beg a comparison with the original, of course, and to do that, I have to discuss their endings. If you don't want a spoiler, stop reading now.
This film is, as you'd expect, far slicker and more loaded with special effects than the original. Statham is far, far more athletic and well-built than Bronson. Foster is grimier and more annoying than Jan Michael Vincent. All of that is pretty much what you'd expect. What I found interesting was how the modern cult of celebrity and desire for sequels affected this newer version.
The original is a morality play in which all the players are bad, and all suffer. In the end, they all die, even Bronson, the hero. Given that we're discussing hit men, that seems morally appropriate.
In the new one, all the players are bad, and all suffer--but Statham survives. Sure, he's been duped into killing both his friend and his protege's father, and he also kills his protege, but at the last second we learn (as if we hadn't already figured it out) that he rolled to safety. Of course he did. How else could there be a sequel? Perhaps more importantly, we as a culture seem to have made peace with very bad people as protagonists for whom we will cheer. We don't mind Statham surviving as long as he looks good and continues to kill only bad folks. I don't have a problem with that per se; in fact, my own Jon & Lobo series features a very bad man and an even more dangerous machine sidekick.
In this case, though, I preferred the original film's ending.