Also it was very helpful for upgrade Joomla 1.6, 1.7 while with standard Joomla update process there where sometimes problems.
Next important feature was update notification in Control Panel.
In Joomla 2.5 there were many improvements but Admin Tools is still helpful.
Lately this tool has been changed to commercial but it adds much more functionality which makes next big step for creating components.
There are still missing some very important options to make easier development of big components, but I hope in near feature it will be added.