According to reports (e.g. digg) Bioshock installs a DRM rootkit on your machine. The original report does indicate that Microsoft’s RootkitRevealer application flags it as such, but it actually looks to be less of a rootkit (i.e. something that installs itself at ring-0, cloaks itself, and makes it almost impossible to remove) and more of a protected service that takes some command line tomfoolery to remove. The service allows non-root users to access the copy-protection functionality (which, presumably does enough funkiness with the drive that root access is required.)
At any rate, consider yourself warned. There’s nothing that definitively states whether or not the service is automatically removed by the uninstaller. Me? I don’t care–I’ll probably just wipe the partition and reclaim the space when I’m done.