Version 1.1 of ASObjCExtras, a free framework that fills in some of the gaps in AppleScriptObjC support, as well as providing some useful extra facilities including methods for efficiently processing lists and strings, is now available from:
www.macosxautomation.com/applescript/apps/ASObjCExtras.html
In particular, it addresses the issue of reals losing precision, and conversion between AS dates and Cocoa dates.