I would find this most invaluable as well... Similarly, I would like the following repeat item options:
- First WORKDAY of the month, that is I want it on the first of the month unless it falls on a Saturday/Sunday
- Last WORKDAY of the month; same deal.
- Repeat every Friday, unless it is marked a HOLIDAY. In that event forward to the next or prior WORKDAY

This woujld make piCal a corporate-grade application. I don't know of any other calendar program that does this.

The next best thing would be this if it were possible:
- Setup a Repeat Series, say repeat every Friday
- In the event a Friday is on a Holiday that month, change the date of that one item and it asks (do you want to change for this one item or the whole series?"
- Similarly, if I delete an item that is in a series, option should be there to delete the one item or the whole series.

Thanks!!!

-Anthony