It depends on how serious you want to be about your coding and what levels you aspire to.

If you only ever use a WYSIWYG then you will be in trouble when something goes wrong - and it will - as you won't know how to fix it.

I'm employed full-time as a CSS/XHTML 'guru' so it would be bad for me to use a WYSIWYG however I do still use the split view of DW when creating HTML e-mails as they still require crappy code to work across as many platforms as possible.