Overall amazing, funny in the right places, full of variety, and absolutely FUN. Highly recommended!
(Note: This review does contain spoilers for the level, so if you think that killing Hitler is fun enough on its own and don't particularly care about surprises, read on!)
To start off, just the reason why you're the ONE guy who's gotta kill Hitler (instead of the allies sending in a whole army to get the job done) is PERFECT. You were originally sent there to assassinate a nazi admiral, only to find that he's already dead-by Hitler's own hand, punished for disloyalty. It's not as if the allies knew Hitler's location and decided to hedge their bets on one guy, it's just a classic case of right place right time! A happy little accident that could very well lead to a dead little dictator!
The level itself is designed phenomenally! From the outside it is extremely well-fortified and crawling with nazi soldiers, perfectly explaining why the nazis would feel like Hitler was safe to stay in there! I mean, Karl (your character) says himself that it's "better fortified than Hitler's bunker"! There are multiple snipers surveying the area, and even a pillbox guarding a tantalizing flank route! And, on top of all of that, alerting the guards while you're outside the building causes the nazis to hit the panic button-sealing the main entrance and sending Hitler and his posse to a safe room in the corner of the map! It makes perfect sense-they may be a bunch of nazi idiots, but they're still capable of acting somewhat rationally! And the secret ways you can get in without using the main gate make perfect sense for why the nazis would overlook them!
From the inside, the level design truly SHINES. The map is a naval base designed for the building of axis ships and submarines-there are workshop areas, a command center, cranes, the works! The whole thing is constructed in a way that contributes to a fun gameplay experience while also making enough sense to not ruin your immersion! Killing Hitler won't be anything like "Oh, look at this conveniently-placed car at the top of this hill! Sure would be a shame if someone were to disengage the emergency brake while Hitler just so happens to be standing directly in front of it!" (looking at you, Sniper Elite 5). Everything in the level just makes you think "Oh, of COURSE this would be here! That makes sense!" In fact, if you alert enemies while you're INSIDE the base, they'll sound the red alert and try to get Hitler to his escape boat ASAP! Because of COURSE he would have an escape plan!
As for the actual killing of Hitler, oh-ho-ho BOY does this level have something in store for you! Hitler will be walking around the naval base, being given a tour of it by one of the officers, while his personal bodyguards walk right alongside him (again, something that just makes sense). Not including the conventional ways of killing him (e.g. just shooting the bastard), the level has about half a dozen ways to put the moustache man six feet under, and each one has an achievement attached to it! And, of course, as with any Sniper Elite enemy, you can shoot Hitler between the legs-and find that, yes indeed, Hitler has only got one ball! (No word on Goering, Himmler, or Goebbels).
Overall, if you're a fan of killing nazis (which you probably are if you're playing the Sniper Elite series), then this DLC is ABSOLUTELY for you! I've killed Hitler more times than I could ever count-shooting, stabbing, crushing, exploding, you name it-and it has NEVER stopped being fun! Both the Hitman-esque opportunities to kill him found in the environment as well as all the other ways you can find to kill him (e.g. placing a land mine at the bottom of a staircase, thus causing the explosion to launch him back UP said staircase) are an absolute joy! The DLC takes itself just seriously enough for you to be satisfied, while not so seriously that you wouldn't be able to laugh with it! Absolutely worth the $10, and even more so if it ever goes on sale!