Slightly off-topic, but still somewhat relevant:
There's a, roughly, two mile section of I-70 here in Denver that I ride fairly frequently that's topped with the despised grooved cement. It's always caused me a small amount of distress while riding it on my 750 with Avon Roadrunners (front and back). The bike gets that typical "floating" feeling to it.
But lately I've been riding the 550 fairly often, equipped with the Avon Speedmaster ribbed front tire, and I have no problems at all on this same section of highway. It's always been said that the ribbed tires are worse on grooved pavement, and it makes sense why that would be, but this has not been the case, so far at least, in my experience.