Apparently, and there seems to be no "catch," if you sign up for the free 7-day trial of IGN Prime (http://login.ign.com/prime/landing) you can get a code for 15% off of ALL Gamersgate purchases. They claim this is permanent... but take that with a grain of salt. You WILL have to enter some sort of payment information (I used Paypal to avoid giving IGN a CC number) and set up an account with an email address.
Once you set up that Prime account, you will get instruction in the upper right to go to GG and enter a code for that 15% discount. You can also click to get codes for King Arthur and Rochard on Steam, completely free.
Now I like IGN Prime, when I was subscribed to Fileplanet. But you will want to immediately go to the account settings in your profile and set Auto Renew to OFF, or you will suddenly find yourself paying for IGN Prime in a few days.
I've recently had some issues with Gamersgate, but this is a no-brainer. You can even pre-order games like Mass Effect 3 with the discount.
Rock, Paper, Shotgun has some more info and a discussion of the process here:
http://www.rockpapershotgun.com/2012/02/11/the-rps-bargain-bucket-longer-subheading-than-usual/#more-93915
Anyone know if this works in the states? When I click on the IGN sign up I don't see anything about the Gamersgate discount :(
Errr... I'm in the US and it worked for me.