Recently our organization has migrated to Now Up-To-Date, and so far we are quite happy with it and the support has been good. However, I have two large iCal calendar files that will not import into Now Up-To-Date. The Now folks have been helpful and suggested that I try a few different AppleScript solutions, but none of them worked.
Just when I was running out of options, I realized that both of these apps sync to Palm devices. So I borrowed a Palm device, reset it to Factory default, then setup iCal to sync to Palm. Then I went ahead and set up Now Up-To-Date Palm sync, and it worked fine. The only issue was that it merged both iCal files to one Now Up-To-Date category; if this is a problem for you, you can always just sync each one separately, of course.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040311190718323