I removed my brain because I was bored. I replaced my entire head with lump of glowing metal because there was nothing else to do. My legs are now pistons because it was the only decision I felt I had to make. My chest is a mass of steel and circuitry because surgically removing my torso seemed like more fun than walking down another corridor.
Much has been made of the moral dilemma at the heart of Space Siege, a sorta-sequel to the Dungeon Siege action-RPGs. It's a similar concept to BioShock's ethical quandary, but instead of murdering little girls in order to gain more instant power, here you're swapping parts of your body for cybernetic upgrades, and losing your humanity whenever you do so.
Or not: you can refuse the upgrades and thus stay in touch with your sensitive side. Trouble is that, as an extension of Gas Powered Game's ongoing philosophy of streamlining RPG memes, there are almost no other decisions to make in the game. Levelling up happens at pre-ordained plot points, new powers and weapons are similarly handed out at prescribed locations and all loot is composited into generic 'upgrade components'. You do get to distribute skill points across an array of stat boosts, but it's rare that you'll notice any significant variance from doing so.