It provides a much better user experience. E.g., you can click, hold the mouse button, and move the cursor. In the original implementation this would select text. Now it behaves like the desktop counterpart. Also, when you click inside the text box it'll automatically open a little tooltip indicating that this text field has auto-completion. Too often this is far from obvious. Also, the text field has a mode in which it acts like a drop-down field with auto-completion.
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We've published the source of our autocomplete fork here:
http://bitbucket.org/twanschik/nonrel-search/src/tip/search/media/search/
It provides a much better user experience. E.g., you can click, hold the mouse button, and move the cursor. In the original implementation this would select text. Now it behaves like the desktop counterpart. Also, when you click inside the text box it'll automatically open a little tooltip indicating that this text field has auto-completion. Too often this is far from obvious. Also, the text field has a mode in which it acts like a drop-down field with auto-completion.