That Google, Yahoo! and MSN would not tell you about (because you already know them yourself):

1. Too many search results and too many irrelevant search results. After spending time on the first few pages of the search results, you don't have time or patience to go beyond those pages.
2. No ability to manage the results by defining context or meaning.  It is not easy to build an advanced search query. Lack of hints for search.
3. No user-friendly visual management with mouse click.
4. Documents are ranked by a search engine according to an algorithm. specific to a search engine, and not specific to your interests.
5. Over-ranked commercial and under-ranked non-commercial search results.