Do you know the ORA- nonerrors?
In one of my script, I am checking at the end for any ORA- error. And if I have any ORA- error, I quit with an error.
So far so good.
Also when I run a report from the shell, I do set the sqlplus settings I like and I expect the script to receive the output with no ORA- error at the beginning.
But watch this !
$ echo "set feed off hea off newp none
conn scott/tiger
select * from dual;"|sqlplus /nolog
ERROR:
ORA-28002: the password will expire within 10 days
XMy password will expire in 10 days. And this screw up my day 
i comletely share your feelings about the expired passwords
Sound more like a functional bug to use an ERROR facility for warning purpose.
Actually there is even the ORA-00000 error that means success
http://download.oracle.com/docs/cd/E11882_01/server.112/e10880/e0.htm
ORA-00000: normal, successful completion
Cause: Normal exit.
Action: None