Usability 
The mobile version of Google search mirrors the simple design of Google's desktop site.
By default searches return combined results from Google's mobile, local, web and image indexes. A mobile phone icon is displayed next to results links pointing to mobile friendly sites. Google identifies mobile sites by a number of clues including the presence of link rel="alternate" media="handheld" headers.
On non-smartphones, once you have performed an initial search, there's a drop down at the bottom of each result page that let you limit searches to Images, Places, News, Blogs or Mobile.
Pages from full-web sites are transcoded on basic devices. On some devices it's possible to disable the transcoder in Google Search's Preferences menu.