Personally, I payed full price for it and don't regret it.
Admittedly there were a lot of hardships at first (before the patches, especially), and the sim requires a handful of mods before it becomes really enjoyable (the TDW's UI mod, especially), but now that all that is in place I am having a great time with SHV.
Granted, I expect that SHIII and SHIV were more accurate sims (though from what I understand one of the biggest gripes about SHV is that flaws in previous versions were not corrected), but SHV has something that I had been looking forward to for a long time: the ability to really take on the role of captain.
In short, you're not the submarine itself, or a synthesis of the entire crew. You are the sub's captain, nothing more. The whole 3D design of the boat and crew interaction is a brilliant idea, and that above all is why I jumped on board (quite frankly, I had never been a big u-boat fan before SHV).
Of course, that feature also needs some modding to be more enjoyable (mightyfine's crew mod, and more crew commands, along with TDW's UI mod), but once that's all in place, the sim is excellent.
As a bonus, get one of the gramophone mods, that adds a bunch of semi-appropriate music. Then you can issue your orders, retire to your nook, and read a book while listening to Edith Piaf.
Itkovian