If there's no money on the line, could you still play poker for real? A lot of people can't, but Stacked forces you to bring your best strategy or suffer humiliation. And if you're not careful, you might actually become a better poker player in real-life after a few severe beatings.
Professional player Daniel "Kid Poker" Negreanu graces the box, but the real star here is the Poki AI, an artificial intelligence research project that has only recently been applied to video games (though you will find it in some tutorial programs costing many times more than Stacked's $30 asking price). The "realistic, human-like" AI can be defined as "play crappy cards and the computer will kick your ass." Seeing as how this is also true in real-life casinos, the claim is valid - and like real people, the game watches your style of play and adapts accordingly. If nothing else, Stacked will make you pay for your betting mistakes in a risk-free environment (until you play online in the Stacked Masters tournaments - but better your reputation takes a hit than your wallet).
That's really the key to Stacked's appeal: it's a far better real-world poker trainer than other games could ever hope to be. Negreanu stars in a series of tutorial videos, but pay attention during play and you'll sharpen skills like calculating odds, detecting patterns and learning to remember your face-down cards - not to mention not playing any two crappy cards just because you "have a good feeling about this hand." For new poker players or anyone looking to improve, it's an excellent tool.