To be honest, I've been surprised at the more or less total lack of Night Stalker. It seems like every time I play him, he's always useful. You can give him an armlet and BKB and he can be a semi-carry, or you can play him almost as a utility/support character, going for aura items and a scepter with gem. Void does a lot of damage on a short cooldown and low mana cost, and his silence is flat-out amazing. I guess he's a little dependent on time of day, but only until he gets some XP. Seems like he could fit into that sort of "utility carry" role that Naix seems to be the poster child for these days.