I hate auto-advancing fields. Auto-focus on page load puts you in the right place to start. Auto-advancing disrupts you in the middle of typing.
I would auto-advancing only if I am creating a form I am certain will be used over and over again by the same person. Even then, I would strongly consider if that is really any better than having the correct tab order defined.
* Worsens the experience of dealing with typos (which are not uncommon) as you've already zoomed away from the field you want to edit
* Risks confusing, increasing anxiety, and possibly generating errors for people that aren't tech-savvy, and for whom spotting the (often very subtle, these days) signs of which field is in focus isn't easy or instinctive.
I would auto-advancing only if I am creating a form I am certain will be used over and over again by the same person. Even then, I would strongly consider if that is really any better than having the correct tab order defined.