Yeah i watched "In Enemy Hands" a few days ago and was pleasantly suprised. Except from the submerched fighting between subs it was pretty authentic i think and i liked the german costumes and actors alot. I watched U-571 after that and it was much worse.
Das Boot's mini-series was 5.5 hours. Though maybe due the way that video is run at a slower speed in NTSC regions I think (something like that anyway) it might be 6 hours in some versions. The longer something goes on for, the higher amount of time that'll be added, half an hour for 5.5 hours doesn't seem too outrageous.