yeah, nothing sexier than a bunch of veins. It's one of the positives about having pigment in your skin. you have the veins, but you dont see the color as much so the blend in.
I dont know how long it takes to see definition change, but I have worked out religiously, five-six days a week for the last year, and I have noticed improvement in the last three weeks since I started cylcling. I think its a matter of new exercise can have a bigger impact in your workouts. its one reasons people cross train, so they can hit their muscles in different ways.