Google added some keyboard shortcuts that help you pick a search result without using a mouse. After typing your query and pressing Enter, you'll notice a small arrow next to the top result. You can press Enter to visit the page or press the up/down arrow keys to select a different result. To open a page in a new tab use Ctrl+Enter and to open it in a new window use Shift+Enter.
The shortcuts work even if you want to go to the next page of results.
If there's an ad displayed above search results, Google doesn't ignore it.
Unfortunately, the currently selected result is not preserved after visiting the page and going back to Google. That's an important feature which was available in the Keyboard Shortcuts experiment.
The support for keyboard shortcuts is not limited to web search results. You can use the shortcuts in Image Search, Google Video, Google News, Book Search, Google Groups and Google Blog Search.