Yahoo tried to improve the mobile search experience, by showing results from the most relevant types of searches all at once. So if you search for a movie star, you'll get a top result from the web (that should be the homepage), images, movie showtimes in your area, news - all in one page of results. This should save time, especially if the results are relevant. Usually, people who search from a mobile phone want fast results, so Yahoo mixes the best answers from different categories.
It's nice that most preferences from your Yahoo account will be available in the mobile interface. You can upload photos to your Flickr account and view other photos, you can read your email, compose messages and search them, read news, get the latest sport results and more.
Google has only two applications for mobile phones: Gmail and Google Maps. The rest of the features could be obtained from google.com, where you have access to search, news and a personalized homepage that can mix all the information you need when you're on the go. The beauty of Yahoo's approach is that you only need one software to get everything. And it's faster than using the mobile web directly, because the application uses caching and background loading to optimize the traffic. Some people might see Yahoo Go as a browser, because you can browse the Internet using the search feature.
Unfortunately, the application works only on BlackBerries, Motorola RAZR, Samsung SGH, and many Nokia phones, but it's a very big step towards a rich Internet experience for mobile phones. Yahoo also became the default search provider for Opera's mobile browsers, replacing Google.