During the Microsoft keynote at CES on Sunday, Microsoft gave us evidence that surprise hit Geometry Wars: Retro Evolved (an Xbox 360 launch title) is headed to the PC (the confirmation occurs at timestamp 44:28 on the official keynote video). No surprise there, because genuine hits like GW are so rare that hay must be made while the sun shines. We've already blogged about a mobile version of the game; a PC version was inevitable.
No word on timing or price, but it wouldn't be unreasonable to expect it to land this year for between $5 (the price on XBLA) and $20 (the price for most "casual" PC games).
[Update 1: noted that confirmation occurs at timestamp 44:28 on the official keynote video.]