Now I am the second. Got your advice, but I didn't take it
I bought the game, started it yesterday.
If you succeed in getting abstracted from your previous SH series-experience, it is quite enjoyable provided you speak German at least at basic level.
In case I expect SH experience I might get as cocky as you.
My first impression:
System stability: quite good. No freezing and thrown-to-desktop symptom yet.. At pause menu with alt+TAB print screen combination, when coming back to continue, it generates a little wave glitch for a second.
Graphics: a bit below SH3 but far ahead of Dangerous waters.
Gameplay: avoiding the unneccessary questions, it is a simulator. Suiting menu music, retro-feeling (WW1) - the latter takes this game to a remarkable level.
Operation: Only German - no other language adjustment option. Tastatur...entshuldigung...

keyboard layout is quite a challenge. One can find it the biggest frustrating factor. Everything is somewhere else than in SH. This is the very part where it is the most complicated to get abstracted from SH. In my opinion they wanted to avoid being accused of copying SH.
Summary:
If submarine-obsessed, it is worth being played with. If not, forget about it.