We all like 3D effects, sure, but ask us to fork out £5.40 to download a very limited retro shooter just to enjoy some nicely-executed 3D and frankly you're asking too much.
You can kind of see the rationale here, though - Xevious is the perfect 3D guinea pig. It's a top-down shooter which plays out over two planes rather than one. Primary fire deals with airborne enemies, while missiles fired at the ground can destroy the tanks and turrets causing mischief below.
The 3D effects are really good, but more importantly the game itself is just too basic to recommend for this price. Beyond the dual-plane gimmick, it's extremely limited, with little by way of power-ups or variation in enemy or scenery. Disappointing.