You can use any of the mod_setenvif directives; Some have more flexibility, some are easier to use. So the choice is a matter of need and personal style.
I assume this is the line that gave you problems:
BrowserMatch "^Download\ Demon" Getout
But that line should work fine. You could also try: BrowserMatch ^Download\ Demon Getout
-or- BrowserMatch "Download Demon" Getout
If neither works any better, then please tell us what is reported in your server error log -- The information logged there is often quite specific and useful.
You may already know this, but just in case: "^" is a regular expressions start-anchor. If it is used, the pattern will match only if the user-agent starts with the specified string. See the regular-expressions tutorial cited in our forum charter if you need more info.