With the Qfusion-based Warsow Linux game, Llano on Catalyst was 39% faster than the i7-3770K at 1920 x 1080, but the i7-3770K remained significantly faster than Sandy Bridge.
With Doom 3 the proprietary Catalyst driver was much faster than the Ivy Bridge graphics.
When running Xonotic, which is one of the most visually intense open-source OpenGL games available right now for all major platforms, at 1920 x 1080 with low-quality settings the i7-3770K was on par with the Catalyst-controlled A8-3870K. The i7-3770K graphics were 61% faster than the i5-2500K and over twice as fast as the HD2000-based i5-2500S.
Now to look at the power efficiency when dealing with Ivy Bridge graphics...