I am a long-time Nagios guy, now working with PRTG. I like it a lot with a few exceptions. I am user to error states being Warning and Critical in almost all monitoring systems. I cannot stand the use of the term "down" for all sensors in PRTG. If I have a file system fill, it isn't down, it's in a critical state. If a printer is low on toner, it's not down!. Does this bother anyone else? And users who get notifications don't like seeing the word "down" either. If there were a way to change this one word, I'd like PRTG a lot more.