I honestly kinda enjoyed the OVA, but do remember to finish SC before you give it a watch. It takes bits of the story from SC and alters it in order to make it work in mere two episodes. Basically, it's just pure fanservice ("omg it's a kiseki anime and omgomgomg that scene" etc). Incredibly well-animated fanservice, for that matter. Like, I seriously hope you enjoy sakuga because you're gonna be flooded with it.
The first half is probably better thanks to being more focused and smaller in scope, whereas the second really tries to condense the plot as if to act as a commercial for the game ("buy the game to learn more!"). A bit of a shame, but hey, it was fun in the sense of a "what if" scenario. I also really dig the character designs, so that's a plus.
Yeah, this happened to me to. XSeed should know it by now, I think (I sent an email).