I have no problem with the 5800k as a cpu in general. It is perfectly adequate if not particularly efficient. It is also decent for gaming when paired with a discrete GPU, although it would not be my choice.
I do however strongly disagree that the APU is adequate for gaming in the sense that most here consider "PC Gaming". i.e. being able to play current and upcoming titles at 1080p at any kind of decent framerate and IQ settings.
Correct, at 1080P it's not a good choice. Where it shines is in areas like for casual gamers who are currently console people and maybe thinking of switching to the PC platform for the Steam deals and don't want to spend a ton of money on the PC.
The 5800K runs games well at 720P and for the most part provides a superior gaming experience compared to either the 360 or PS3. With Steam Big Picture mode and the increasing controller support for new games this is a real alternative to console gaming....plus it's a PC so it does all of those things as well such as being able to mod the games or download the giant texture packs for games like Skyrim etc.
I'm using a 5800K for my HTPC. I have over 200 steam games and have installed and tested around 30 modern PC games so far on it. Almost all of my games ran perfectly fine (to me that's basically default settings maintaining at least 30FPS) the only game that I struggled to play where I had to really lower the details was Farcry 3.
Just the other day I picked up a second hand 6670 off Kijiji for $40.00 and plan on adding that to the HTPC for dual graphics which should allow me to play some of the more demanding games.
Anyway, as we know everyone's needs are different but I believe AMD is targeting a large part of the market with these cheap APU's and they offer decent flexibility considering options such as dual graphics as not to mention a few APU upgrade cycles being planned for socket FM2. It does not look like Intel will have an answer until Haswell although I'm a little sceptical they'll have anything around the $100.00 price that will be as well rounded as the 5600/5800K.