Hexblade is great, and I have personally played it several times, and I have it in a gestalt character I'm playing right now. Its not powerful by itself, but the curse is lovely, and it has some really nice abilities.
Samurai is terrible. Its a base class designed to dual wield Katana/Wakizashi. Wow, Ranger exists already, hello. Terrible Terrible class.
Swashbuckler is a light fighter, and thus, it isnt good. But its ok for what it is, and like all the above people, if you combo it with rogue, it isnt so bad. Still, its a 3 level dip only for sure. Also on the subject of Swashbuckler, I can't understand why it doesnt get good fort + good reflex. It isnt like its more powerful than Ranger.