One popular example for how enthusiastic Intel was about performance optimized OpenCL drivers could readily be seen by running Luxmark for example. This raytracing benchmark utilizes OpenCL-enabled processors, no matter what kind of beast they are. When you're using a recent Radeon graphics card in your system, chances are that you already have an OpenCL-1.2-enabled driver for your central processor installed - the one that comes with AMDs Catalyst driver package.
This is not a bad choice by any means, considering that the AMD-optimized drivers outperformed the Intel ones that were available with their 2012 OpenCL SDK by a wide margin. We're talking in terms of 50 percent higher performance here, mind you.
Enter the Intel OpenCL SDK 2013 Beta. Not only enables this version (non-conformat, but enough to get your juices flowing) support for OpenCL 1.2 on CPU devices, it also makes use of the integrated GPUs, provided you're using a compute-enable device from Intel's third-gen Core line-up - Ivy Bridge or Core-i3/5/7-3k.
I have run a few tests with this driver, which is labelled as version 18.104.22.168537 and got the following results running Luxmark 2.0 in x64-mode on a Z77-based, overclocked Core i7-3770k at 4500 MHz and some DDR3-1866 memory.
As you can see, Intel really made use of their processing ressources and easily increased performance by more than 60 percent topping slightly even AMDs improving driver, which is getting better and better as well but which has a very solid performing base, where massive increases are rather unlikely.