I've used it a few times in the past and had no problems (apart from forgetting my password!). If I remember correctly, I registered as I purchased, I didn't need to contact VISA separately.
I have used it on a few sites and got the impression when I first registered (and that is a couple of years ago) that it was going to be common practice everytime I used my card on the internet but it is far from it. I am surprised by how few sites use it.