Let me state:
I'm a BIG fan of the SH series. Been with it since SH 2, and each SH game since III was a first day purchase for me. III was stellar, IV was buggy, but was excellent after being patched.
SH V was also a first day purchase. And it was horrendous.
I cannot begin with how bad this game was, except to say almost in every conceivable way, it was a major step back.
I could go on at length about the horrid technical performance, the visuals that were actually WORSE than SH IV, the MYRIAD bugs and glitches, the poorly implemented and intrusive DRM, and some of the worst, most god-awful AI (for enemy ships) I have ever seen.
But what actually made the game simply unplayable for me was, inexcusably, the actual design decisions they made. This is the epitome of a "dumbed-down" game, which goes completely counter to the series goal as a simulation. Everything just feels like they were trying to lure in console gamers who have no real interest in sub warfare or realism. Linear style, far less freedom, dumbed down options and features, terrible interface. It's just a total slap in the face to fans of the series and anyone looking for a competent sim.
It's made doubly sad by the fact that it's dismal performance probably ended the series as we know it, and it's sad this is the last game we have to remember the series by.
I haven't touched the game since a month or two after its release. I have no idea what the fan support is like and whether there are any mods to fix all the issues, but I somehow doubt it.
I would DEFINITELY recommend getting the SH IV pack (with expansion), as well as SH 3, and enjoying all the mods and content for this wonderful games.