Let me be the cynical bastard and say that the reason the iGPU wasn't tested is because Michael is willing to give AMD time to fix their fglrx to make it work with APUs ?
I've bought an A10-6800K last week and it helped me cement my overall impression of AMD's products : superb hardware, shit drivers. Unfortunately, someone needs to tell the wonderful VHDL-wielding people at AMD that hardware is nothing without the software.
Last year I bought a Trinity-based laptop and I still can't make it work OK-ish in anything but straw-man Phoronix 3D tests with 2000-era engines. I have to disable the crossfired dGPU in the notebook to make it work OK and, even then fglrx still has a lot of problems running anything more advanced that a community-modded Quake 3 engine.
Similarly, I borrowed a HD7750 for the desktop A10-6800K, disable the iGPU and it seems to work ok in most Steam games ( you know, *REAL* tests with high performance, modern game engines ). Remove the dGPU, enable the iGPU in the 6800K, clean and re-install fglrx and ... kaboom ! utter shit ! corruptions in TF2, Portal, The Cave, Oil Rush ... you name it. Yeah, it works with some primitive OpenGL engine from the Phoronix test suite, but then, I would have bought a 5th hand pentium 4 with an AGP graphics card for those kinds of 3D workloads.
Also, I removed fglrx, disabled the iGPU, slap in a geforce 450, installed the Nvidia blob and everything 'just worked'. Every single game from Steam worked flawlessly, Unity builds for Linux worked flawlessly.
For Unity fans, make a moderately complicated scene, with FX, and export it to Linux and Mac. Run it on Linux with AMD fglrx and an APU and then on an iMac with a 6xxx AMD card. Linux fglrx sucks big salty balls, Mac driver works flawlessly.
So much for tin-foil hat conspiracies about Nvidia-optimized games ... Clearly AMD makes more profit from Game coupon bribes for their cards ( if they are so competitive against Nvidia ( or Intel ?? ) why bother with the Game coupons ? ) and ferrying game 'journalists' to luxurious exotic islands for ( linux-incompatible ) product launches. Intel might have robbed them of their market share with bribes and the like from the 1B$ fine scandal, but, man, AMD has some shitty software developers over there ... Lemme' guess, Linux drivers are 'managed' by the Germany team, but the development is subcontracted to the Ukrainians for Luxoft ?
This was my last AMD product purchase. I can't believe that a company this side can't get its shit together and make drivers for their own products. Night after night, after 10-12 hours at work, I waste time trying to make it work when their competitors' products work 99% out of the box.
It might be too late as you've already got the 450, but before you give up on that APU you should REALLY try out the latest open source drivers. I'm running an a10-5800k myself, and suffered with fglrx for a while, so I know what you're going through. The Free driver absolutely destroys FGLRX is every way possible, and will run most games at a higher frame rate. The games that technically have a lower framerate will still perform better, since there is no more stuttering or random fluxuations in fps. Valve games especially run great. A bit of warning is that the Buddah engine Double Fine uses in The Cave and Brutal Legend currently freeze due to a Mesa bug, but overall more games run fine compared to FGLRX.
I'm running Arch, with the 3.11 kernel and 9.2 mesa. Basically just a standard install fully up to date. You will have have enable dpm with the kernel parameter, and enable the SB shader optimization. That's basically it. The APUs are easy since they require no microcode, and perform great with R600. With the next kernel release, those two steps will probably not even be necessary anymore.