Impressions pieces, because they often represent only about an hour or two of gameplay and about a half hour (about the total length of time a writer can stand to be away from a new game) of writing time, generally fall into two categories: the love fest and the trash piece.
This is because most games will generally tell you all you need to know about them in the first few minutes. It's either brilliantly conceived and can therefore do no wrong on that glorious first day it's in your hands, shiny new and still smelling like the inside of a new Buick; or it's deeply, deeply flawed and playing it is keeping you from doing something more fun, like cleaning the bathroom.
Generally, most games will even out somewhere along the 10-hour mark, and a great game will mellow to simply "good" and a horrible game will develop some enduring trait, raising it's mark to something along the lines of "mostly bad." Rarely will they remain at the polarized extremes presented in the first few hurried hours of play.
I've just played four hours of BioShock, and I can say one thing for sure about it: It still smells like a new Buick. In a cunning move on the part of developer Irrational, they allowed me to play the first half hour or so at this year's E3 event, which meant that as soon as I fired up the game this afternoon, I already knew how to play and how to survive those first few encounters. So I had a little bit of breathing room to sit back, try new things and take in the spectacle of it all, and make no mistake, if any game from the past couple of years could be called a spectacle, BioShock is it.
The game opens, literally, with a bang - your airplane crashes - and you find yourself immersed in the world of Rapture before you even know who you are and of what you're capable. This, like so much else about BioShock is a stroke of genius. Regardless of whatever preconceptions you bring with you into the game, your character is a blank slate. You're not a space marine sent to eradicate evil. In fact, in the murky world of Rapture, it's hard to tell exactly what evil is. Rapture is a ruined monument to man's indomitable spirit; around every corner are examples of man's hubris, scenes from the fall after the pride.
It's also one hell of an action game. The enemies are smart, sneaking around corners to surprise you, running to heal themselves and lobbing grenades when you duck under cover. You can outsmart them, by setting traps in doorways, lighting fire to a pool of oil or drawing them to water, then electrocuting them, but it feels like you're outsmarting them and not simply taking advantage of bad coding; surviving, not hacking. And speaking of hacking, you can do that, too. Gun turrets, robots, safes and vending machines can all be hacked if you don't mind the pipe-fitting mini-game. If you do mind, you can pay the price in money or blood, but for those who'd rather use their minds, the hacking game is a nice touch. It reminds me of a game called 2010 for the Colecovision. But in Bioshock it's more fun, and actually has a point.