Everybody is trying to figure out how to make a V5 work... well... ask VW group. They are currently selling some of their cars with such engine. I know thats no race engine, but for what Ive read is supposed to work really good. That engine is a narrow V. It is basically the same engine as the VR6 but with one less cylinder. As a matter of fact its called VR5.
Due to the fact that the VR5 engine has a narrow V configuration, all the stresses are greatly minimized. And its behavior falls between the one of a V engine, and an inline engine.
Obviously the engine from Honda has a bigger V, but that not something it can not be taken care of with the proper firing, and a properly design balance shaft (which yes they rob power, but they also smooth the power delivery). Or, as some people is pointing, with pistons of different sizes.
These new engines are going to have so much power anyway, that I dont think the engineers mind loosing a little bit in favor of a smother power delivery (which is the main advantage of these engines vs. the 2 strokes).
I can wait until the start releasing more info about these new "toys".