For the search phrase 'advice and tips on SEO' my site comes out #2 (Google is #1). This is the page title and H1 tag.
Google tells me, though: "The "AND" operator is unnecessary". But if omit the 'and' I enter 'advice tips on SEO', my site drops to #3.
Further, if I drop the 'on' (what I would consider another stop word), my site drops to #25.
In MSN Live Search my site remains at #11 with all 3 variants.
1) Google does appear to be influenced by 'stop words.
and more importantly:
2) What would normal humans enter in google: 'advice and tips on SEO' or 'advice tips seo'?