I know this topic is a couple of months old, but I finished the game yesterday and I have to admit it was quite a bit of fun. A little too short for my taste though, playing on the veteran level on and off over the span of a week and a half I finished it in about 10-15 hours. Looking for the secret "Kilroys" and "Recon Points" on each level could probably add a couple of hours of playtime, but for the reward you get it just didn't seem worth it to me.
The kill-cam or whatever it's called was my favorite feature, getting a headshot and then having the game go into slow-mo and zoom in to see the shot impact and subsequent blood-spray forced an evil grin onto my face each time it happened. Same thing with grenades or bazooka rounds, seeing a nazi fly through the air in one direction, and half of his skull and one of his legs fly in the other direction with plenty of gore in between the torso and body part was amazing!
I'll probably play through one more time now that Authentic level is unlocked.