Cool script. I did have to make a correction/addition to avoid trying to string together a NULL in the middle of the schedule description. The case statement that would put an "s" after a freq_subday_interval greater than 1 needs a default zero-length string.
I added this ELSE line (it's near line 150 in the original script......)
+ CASE
WHEN msdb.dbo.sysschedules.freq_subday_interval > 1 THEN 's'
ELSE '' -- Added default 3/21/08; John Arnott
END