Roughly a year ago I implemented the Autocomplete plugin developed by Jörn Zaefferer for one of our systems. Since then, this plugin has now been integrated into jQuery UI and the original version has been discontinued, with no new development or support. The author made available a simple guide for migration, yet a few of the features were discontinued with no migration path clear. Per his own post:
autoFill: Gone with no immediate replacement available, for good reasons: The default behaviour when selecting items via keyboard now puts the focussed value into the input, like the Firefox Awesomebar does it. It's not the same as what the autoFill option did, but there should be no need to recreate that effect.
mustMatch: Gone, but easy to implement with the select event. Once more, the combobox provides an example for that.
selectFirst: ...