Search engines like simple html code. What they don't like is stuff they can not read. Framesets, Flash, Shockwave and Java ( not to be confused with Javascript ) can all cause confusion to the search engines.
If they can not read your site they have no idea of how to index your pages. In turn this usually means your site does not do too well in the search results. At Duo we use flash, shockwave and Java applettes to keep websites looking interesting. However we always make sure that the important information about every page is readable by the search engines. Plane HTML by itself doesn't always make a very interesting site. Using all the technologies with the search engines in mind can create sites which do well with both Google and your readers. We also know how to use Meta tags correctly to make our sites even easier for search engines to spider and index.