Steam is currently offering the game at a 25 per cent discount, bringing it down from $29.99 to $22.49.
Steam has also slashed 50 per cent off The Witcher: Enhanced Edition Director's Cut. The offer ends October 20, at 10am Pacific Time.
The Witcher 2's Mac release on GoG also marks the start of Mac support on the digital service. GoG now has a selection of Mac titles available for purchase, a full list of which you can see here.