DragonKing: I'd say the biggest drawback of ShogiVar is that it's not two-player :) I want to play real people! (And yes, ZoG supports two-player, but only in real time...I don't have many continuous stretches of time to devote to, say, Chu shogi or larger)
ShogiVar is a great piece of software though, and it's good for getting familiar with the pieces.