Whether or not this is a good thing depends entirely on how much you like the Call of Duty titles to begin with. If you've played any of the previous games you'll feel right at home in MW3—a fact that actually caught me by surprise, given that I'd skipped Modern Warfare 2 and hadn't actually played a CoD title since 2007's Call of Duty 4.
If you're looking for a game that fundamentally moves its own bar forward or offers significant single-player innovation, this isn't it. Players who thought MW2 and even the original CoD 4 were tired rehashes of stale game mechanisms will find no reason to change their minds. Gamers who enjoy the formula enough to slip into a new title, on the other hand, will enjoy the experience.
MW3's single-player campaign is fast-paced, exciting, and short. It can be beaten in five hours or less on a first play-through. In this case, that's a good thing—but only because the game's plot is so threadbare, it could scarcely sustain much more.
Modern Warfare 3 eschews character development or the need for thought in favor of building on MW2's already incomprehensible mashup of ultrationalist Russians with nonsensical plans for world domination. All of this is wrapped around the familiar returning figures of captains John "Soap" MacTavish and John Price. MW3 picks up where Modern Warfare 2 left off and focuses on the two men's effort to find and kill Russian ultranationalist Vladimir Makarov. It's also an excuse for blowing up the Eiffel Tower.
Games with great plots generally get away with short campaigns, but five hours of gameplay for $59.99 is a dismal value proposition, particularly since there's no great storyline or storytelling anchoring the blink-and-you'll-miss-it whirlwind tour of international locales Infinity Ward wanted to blow up.
Is it fun? Absolutely—just like the dozens of other shooters (and a solid handful of CoD-style shooters) available for $9.99 - $19.99 on sites like Steam. There's nothing in the single-player campaign to justify a $59.99 price tag unless you're a die-hard CoD fan who absolutely must have his fix—in which case, you've already bought the game.