It's referring to the nick as well, adding the ! forces the identifier to be evaluated when the time executes rather then when the timer is started. I don't know why I used that instead of just using the nick, probably just because it's shorter and it's habit I guess.
~ Edit ~
From mirc.chm:
You can force identifiers to be re-evaluated when used in a /timer command by using the
format $!me or $!time.
