Buy it.
Samurai Gunn 2 improves on its predecessor in every way, while also adding new core gameplay mechanics, a new visual style (while remaining wonderfully old-school), character lore, and online multiplayer with private parties and matchmaking; it is a must-buy. The original design was to be fun at parties, and it has definitely retained that DNA.
And if you have never played the original? Even better. This is a real fighting game; it requires fast reaction time, precision, planning, strategy, and knowledge of the characters' abilities. If you enjoy fighting games in general, you'll enjoy this.
High-level play is intense, and weirdly graceful, like a dance. Scoring a kill pauses the action for a moment, giving you enough time to plan your next move.
Three- and four-player multiplayer is pure delightful chaos. Think "Smash Bros," but feel "Kill Bill." The most fun I've had with this game is with a full party. One-vs-one duels tend to be a bit more thoughtful, but not really any slower.