We've seen good results with keywords in the URL, if no reason other than to entice searchers to click your search listing. Human visitors are becoming better at ignoring spam in search engine results, and are looking to important clues in your listing. Keywords in metadescriptions, titles and URLs get clicks. Along those lines, we just blogged this morning:
9 Tips: Treat your
SEO like a PPC Campaign
As for the actual questions, I think inbound link anchor text and titles are the most important
SEO elements to worry about - as long as you don't have any barriers to the googlebot accessing your site (like javascript only navigation, etc.)