Google is continuously accused that it didn't improve its search engine (some even say Google doesn't care about search anymore). So how is Google search better than two years ago?
Google's index updates faster
While two years only very popular sites were updated every day, now a lot of sites are updated every 1-2 days. A search for [Google Marratech] returned 8/10 results about Google's latest days in less than one day after Google Blog mentioned about it. Yahoo and Live Search returned no result about the deal in the first page of results.
Closer to the natural language
Google no longer tries to find the exact keywords in the documents. It uses stemming so you can find documents that include "flower" even if you search for "flowers", it includes synonyms for the keywords and expands abbreviations. If you search for [Aretha Franklin birthdate], most results' snippets have "birthday" in bold.
Google Co-op aims to label high-quality web pages, so users can refine their queries. While there are only 6 general topics, users can label any web page for their own custom search engines.
If you have an account, Google can record your queries and the visited web pages to improve the quality of the search results. This way, Google can do a better job at disambiguating queries and putting your query into a larger perspective.
More specialized search engines
Book search, blog search, patent search, music search, news archive search and more. All these search engines allow you to focus on different kinds of information and get the best results from their limited scope.
Unified search engine
Google brings more information from its specialized search engines using OneBox results and PlusBoxes. Google also wants to include results from other search engines directly in Google search: the first stop will be news results. Other plans include results from book search. The goal is to have an universal search engine that includes every useful information crawled by Google.
Outside the SERP
Google experiments with interesting ways of integrating search results into content that adds value to a site. AJAX Search API lets you build web applications that take advantage of search results.