I just did some more tests regarding schedule/WOL and dependencies on refresh, current goal was to find a way to upgrade some WXP SP2 workstations to SP3 (out-of-lights unattended).
So I tried a schedule (pushing immediately worked without problems):
Date/Time set, Wake-On-Lan, Install and Launch immediately was checked.
I found the workstation booting up and sitting...nothing happened...
So i used another workstation, used the same settings but enabled "Process immediately if device unable to execute on schedule" - voila :)

I don't know if it's working as designed but it's always a good idea to consider what happens during refresh:

- While the bundle is assigned - the workstation doesn't know about it
- the WOL wakes up the workstation
- after workstation is up the agent will refresh (default delayed)
- the bundle schedule time is in the past now... (so the option above is needed to get it to work)

Hope it helps