I have seen some of the most "off the wall" META data you can imagine. Looking at pages that actually do get top rank in SERP, I find that page content is what got them there. These "extra" tags seem to be ignored by the major SE's.
As stated above - solid
SEO will get the best results.
- Page URL
- Page title
- Page description
- Optimized visible text (headings, sub-headings, lists.....)
- Link text (internal and external)
- "alt" attributes
All the standard stuff without making up things the SE's just won't use.