Stability-wise we have very little, actually nothing, to complain about as at half load, say 300~350 watts, voltages remained to drop dead in sync. But we'll trust that some other reviews will offer you some ripple tests yet have no doubt the product will come out totally clean. Kick-ass is obviously the option for four rails, the tested model has enough power to handle a high-end graphics card.
Guru3D has published a review of the be quiet! Straight Power 11 Platinum 650W. He likes the stability and specifications of this power supply and also positively comments on the design aesthetics. If you're in the market for a Platinum power supply, this model ticks all the right boxes. The result is a Recommended award.