The early reviews starting to trickle in are pretty positive. ShockTillYouDrop's review was glowing, as they previewed it at SXSW either yesterday or today.
As for the movie being shelved... it was likely due to MGM going bankrupt when they were initially going to do that ill-advised 3D conversion (and not because the movie tested poorly). And then the completed film got shelved because MGM took a long time getting its debt consolidated. Then when it emerged from bankruptcy, the new CEOs decided to unload Cabin and the Red Dawn remake to other studios (Lionsgate and FilmDistrict, respectively).