I’ve put together a collection of Objective-C files, Myriad Helpers, to make some aspects of AppleScriptObjC easier for AppleScript scripters to use.
The files include a class of assorted helper methods, plus a series of extras that make it easier to use path controls and date pickers, as well as alerts, open and save panels, and windows, especially as sheets. To use them, you just drag them into your projects.
For more, go to http://www.macosxautomation.com/applescript/apps/helpers.html. The download link is at the bottom of the page. The files are included in a sample project, which includes examples of their use.