As someone who builds and owns exclusively AMD, I'll tell you my take:
OEM systems:
Crap OEM designs, no way around it. The APUs need bandwidth to shine, and when the OEM systems come with single channel slow memory, the APU is starved. Furthermore, AMD cannot match the kickbacks the other guys are doing, so the APUs end in very poorly speced machines. I have been looking for months for a laptop replacement for my HP probook 6475b. A Beema in a 12.1" chassis with M.2 slot, IPS 1080p screen and backlit keyboard would be calling my name, if it existed. The closest thing to a decent design is the HP elitebook 725, but lacks the M.2 slot, and it is expensive.
In the OEM desktop systems it is a similar situation, the APUs go into the lowest speced systems, so the end users associate the poor performance to AMD, when in reality a system as poorly configured wouldn't be much faster with an i7-4790k instead. Now, in this regard of OEM desktop systems, AMD is not totally exempt of fault. If you give a low cost very low performing option to the OEM, they will take it everytime. The E2s and similar should not exist at all. Furthermore, the AM1 stuff should be Athlon quad cores 2GHz and above. But if you have a dual core at 1.3GHz for cheaper, the OEM will take it. Shady28 and other have already touched this point.
DIY Retail:
Price: The A10-7850k APU is a lovely piece if silicon, but at its current price, it is hard to pick it over a FX6300 + R7 250X combo that will run close in price to a A10-7850k + DDR3-2133 RAM. I am using a A10-7850k in my desktop now (had a FX8320 + HD7970, wasn't gaming at all so downsized) I got the Kaveri in one of those crazy MC bundles, but if had not been that way, I might have stayed with the FX8320 and probably change the video card. The A10-7700k is reaching parity in price, but needing faster ram to shine, it is a hard proposition for the DIYers. Until the APUs with a FM2+ mobo reach parity with a FX6300 with a AM3+ in price, they won''t sell that much.
Performance is perfectly fine, and before the pussy and his minions of fanboys come claiming that APUs are slow, for the vast majority of the population they are perfectly fine. They multitask better than the dual core of the blue camp that these fanboys try to push, and will perform better in typical household use (read: Like 50 facebook tabs open, have better hardware acceleration for flash, used in so many web games and better video decoding) Don't believe my claim? How about you go and use BOTH? Not scour the web for academic numbers and starcraft babbling, test drive them yourself in typical household use, see what you think.
An APU in a decently speced system will please almost any user. Heck, my Probook feels faster than my work machine (Dell precision M4800) and I know that benchmarks wise the M4800 should murder it. Both have SSDs, but something as simple as the right tweaks means that while one is dragged down by the corporate bloatware, the other one runs freely.
If you own an APU, have fun with it. If you don't, you want to try one.