The Saboteur seems to combine Assassin's Creed, The Godfather, and Grand Theft Auto into one, but ultimately fails.
I'll go straight to the pros and cons before I get into what I really think of the game.
Pros:
Amusing main character with humorous lines complete with a thick Irish accent.
Story is mildly interesting, but nothing breathtaking.
Decent visuals.
Cons:
Glitchy. I'll delve more on this later.
Buggy AI.
As been stated in previous reviews, inhuman ability to soak up more ammunition than a tank.
I'll just get right down to it, seeing as how I suddenly can't think of proper things to list. This game is glitchy. During my 10+ hours of gameplay I have had 2 game-stopping glitches which made me have to start from a previous save-point due to being stuck, a glitch where I attempted to grab someone getting into their car only to make me stuck in a pose of holding an invisible person (the only way out of this was to either reload or get luckily hit by a car, I guess that's lucky.), and around 2 crash to desktops with no error message (though this could simply be on my end, so I will not blame the game.)
Aside from the glitchy gameplay, the climbing mechanic is very jittery, you will find yourself flopping around like a fish and yelling 'Bloooody heeeeellll' when you realize you can't grab onto what you just jumped at and splat.
The driving in this game seems to have taken a step-back in gaming, every car feels like it's a box and collision is very stiff. I also see no reason why the car which I just drove through a steel gate can not plow through a bush while driving at full speed.
In short: The high-point of this game for me was Sean, the main character, stating the race car Aurora was fastened "Tighter than a nun's arse."
If you have a Nazi shooting urge, by all means give it a try. It is still a mildly enjoyable game if you are not too strict with getting angry with glitches and jittery climbing mechanics. If you wish to play this game for a new Sandbox, it is fairly decent, but I would recommend Grand Theft Auto over it. You want to climb buildings? Assassin's Creed or even Prototype(though far less realistic) would be able to fit your fancy.
All in all, if you have a chance to pick it up for cheap, go for it. Full price? I do not believe it's worth it.