I know it's been mentioned before, but the one thing that turns me off from SH4 is the radar. I've been patrolling in early war S-boats, as using SH4's radar makes me want to throw things across my room. SD and SJ NEED to detect targets appropriate for the radar type only (no SD getting surface contacts). Crew reports also NEED to differentiate air from surface contacts. Also, I don't know if it's only me but the range setting in the PPI SJ station is difficult to make out. Oh, and my SJ radar seems to turn itself off shortly after switching it on. And the interface doesn't allow you to switch the radar on/off or manually control the SD unless the SJ is installed. The original Silent Hunter had great SD/SJ implementation.
http://www.valoratsea.com/radar1.htm
Gripe finished. Other than that I'm having a blast playing, it's 4am here!
PD