The US submarines interface in SH4 is in my opinion a very good one, easy to use and clear. It also adds a HUGE advantage for manual shooting when compared to SH3: It allows you directly input masthead heigth in the stadimeter, instead of following the stupid and long process of having to identify a ship before that. It is beyond my understanding why they put back that absurd interface in SH4 when they added the U-Boats, but probably due to lack of time I suspect. Without the newer interface and GUI mods for SH3, I probably wouldn't also play the game, and hence I do not play the Uboats part of SH4. But now there is finally a mod that provides an intuitive and easy to use interface, as I like it:
http://www.subsim.com/radioroom/showthread.php?t=152590