Yes, of course. Why wouldn't it be?
I'm happy I can use text strings in that function... just for a moment got nervous that it might be 'unsupported' usage as it's not in the function reference documentation.... Not to worry :-)
To add to what Mike said...it's actually one of the things that makes it soooo powerful.
You can also use it to sanitize a list that may have stray line feeds in it.