If you use the styles in Word, you can save the document as an .rtf format, and when you open it into PowerPoint, it will import into slides based on the styles used.

e.g. I usually use the standard 'Heading 1', 'Heading 2', ... etc., and when you import into PPT, 'Heading 1' will be in the 'Title' placeholder, and 'Heading 2' will be the first indent level of the text placeholder, 'Heading 3' will be the second indent level, 'Heading 4' the third indent level, and so on.

Each occurence of 'Heading 1' will break to a new slide.

Once I import the text, I select all of the slides, and reapply the template to those pages to format the slides using the current slide master.