Cor, that's a leading question! I've been looking for sensible "real world" benchmarks. In the absence of Steffen's (he's got copyright and time issues), I had a quick play with Paul Vigay's graphics test on the A6 (currently stopwatch times, I'll release "officially" when I can prove them absolutely). Iyonix times from Paul's website.
Loading image was 2.6 seconds (Iyonix 2.51)
Rotating image was 4.5 seconds (Iyonix 9.09)
Unsharpen mask was 117 seconds (Iyonix 74.91)
Scale was 2.2 seconds (Iyonix 2.26)
The A6 seems to perform faster than the Iyonix when it's "shifting data" with little transforms (eg when you're scrolling around a large DTP document); The Iyonix scores better on cache-based repeated operations where more instructions act on each bit of data (which hits the long pipeline on the A6 reasonably hard).
Your percieved speed of a machine will depend very much on the profile of what you do with it. The A6 subjectively feels slickest for many "user" tasks, but YMMV and I'm biased