It mainly helps keep the sweat off the steering wheel so it doesn't get slippery in my hands. I never really did a before/after comparison in terms of lap times though...
I have a set of FET Sports gloves which I purchased on a trip to Japan. They aren't fire resistant so I guess it's more for street or karting use. The suede material is very thin and hugs your skin so you can feel the wheel very well.
