As mentioned, I'm pretty sure we've chatted about this more than once before, but anyways:
Within reason (i.e.: not as prominent as Chelsea) I don't find visible veins distracting, though I don't miss them either on breasts where they are NOT visible. I have never personally experienced breasts with veins so prominent that they are raised above the skin surface (as Chelsea's are, or arm/leg veins on body builders) but I don't think it would be much of a turn-on for me personally.
As far as a previously expressed opinion to the gist of Chelsea's veins being visual evidence of her going where no breasts have gone before... I understand the whole concept of visual evidence being a turn-on (hence the popularity of facial shots, etc...) but to my mind, Chelsea's breasts ARE going where breasts haven't gone before, in that they are gradually becoming less and less breast-like in appearance. I find the rest of her quite appealing (though some have criticized her rather longish face and lippy external genitals... I think they both look great) but her implants really do very little for me... what appeal she has to me she has in spite of her boob job, not because of it.
JMHO.