This APU gets me really exited; like Dave also said, its the first truely heterogeneous processor out there, with loads of bandwith and tons of calculating power, and for the first time, developers will be able to effectively use it.
Why?
Compare it to your PC; It might have a stronger CPU, and it might have a stronger GPU, and it might even have more Bandwith in total. But thats not where the true strenght of this new chip lies.
Its in the fact that both CPU and GPU share the same (big)memory space and are connected with really low latency. This means that developers can effectively distribute computing tasks across both the CPU and GPU parts, without having to worry about things slowing down tremendously because of the latency from things like PCI-E and the copying of data between the two pools of RAM.
Sure, in the end PC's can probably still deliver the best graphics possible, because there is no way a console can cost-effectively compete against the brute power you can stuff into a PC. But if you want to make really revolutionary games, with stuff like real world physics, AI with actual depth and truely immersive gameplay, at the moment PC's dont stand a chance in their current form-factor.
Edit:
Larrabee was silly, but the fruits of it (newer Intel graphics) was definitely worth the research money imo.
I thought Xeon Phi was the current larrabee? Iirc Intel has been quite succesful at marketing it as a scientific co-processor.
Source