Title says it all.
In terms of the UCs and larger campuses, I would say no. In terms of smaller private, I think it can have an impact as their smaller size makes it easier to track and it shows desire.
There is one good outcome of a visit and that is to meet an admissions counselor in person. This will give you a specific individual with whom to communicate and this could be advantageous if you are applying to a school which has limited transfer acceptances.