A 2K Forums thread on the matter has exploded since the underwater shooter sequel was officially released yesterday, including mentions of buyers remorse, an unofficial workaround, demands for a patch, and links to the inevitable petition.
"Not supporting the controller was not a decision that we made lightly," community manager 2K Elizabeth responded, with the company having explained:
We made quite a number of significant changes to UI / HUD for the PC version of the game. The decision was made early on not to support controllers at all in order to ensure that we got the mouse and keyboard control absolutely right. This of course required a redesign of large parts of the UI and the player HUD. For example, we removed the Weapons and Plasmid Selection Radials in favor of a custom created Weapons Selection Strip which more accurately reflects the keyboard layout.
Central to the complaints is the fact that the original BioShock PC supported gamepads in addition to mouse and keyboard, complete with a UI for either control scheme.
As one would expect, the PlayStation 3 and Xbox 360 versions of the sequel use the console's respective controller, but can not be played with mouse and keyboard.
The release of BioShock 2 also brought with it complaints that the PC version doesn't properly support widescreen resolutions, though a fix is already on the way.
Thanks to Chris (not the one who wrote this article) for the heads up.