If you like the RTS genre at all -- particularly Blizzard's past games -- you're going to get your money's worth. Starcraft II has, hands down, the best single-player campaign I've played in an RTS game. The mission objectives are always creative and unique (besides, of course, the mandatory "defend your base" missions). From robbing trains, to exploding suns that slowly scorch everything on the battlefield, to fighting Zerg-infested humans who only -- and always, instead of the usual mostly -- come out at night on a planet with incredibly fast day and night cycles, the next mission always provides something new and exciting.
Nor is the campaign short -- something I feared after hearing that Starcraft II's story would be broken up over three releases (one for each race). I'd guess it took me between fifteen and twenty hours to complete on normal difficulty. And achievement whores like myself will have a lot fun/misery completing the game on hard to pick up the more challenging achievements.
So, is the game that different from the original?
Yes and no. The most simple answer I can give is that what's featured isn't that different -- most of the units and structures for each faction return, with a few deletions and additions -- but how everything works feels overhauled, tweaked, refined. I spent a few hours with the first Starcraft after beating Starcraft II's campaign, and the experience felt very, very cumbersome in comparison to its successor.
The single biggest -- and most welcome -- change is the removal of a unit cap on each hotkey. Your entire army can be controlled with only one hotkey. The A.I. for your units has been drastically improved to accommodate for this: the units place themselves where you want them to go with a lot less effort on your part, without it feeling like the game is doing all the work for you. And thank the Maker that science vessels will no longer charge blindly ahead of slower units -- and they're finally smart enough to effectively retreat from enemy fire. That alone is worth sixty bucks.
Having one big army assigned to a single hotkey might not make for the most effective army, but for people like me who can't keep up with the pace of each round's endgame, it's an incredibly helpful option.
Going to get back to the game. Possible updates to come.