" for something other than printing to screen?"
Well, usually, I see it used to get the names of the ports to open...
I don't know Serial enough to answer the other question.

That how in using it in my sketch it gets the list of serial ports and displays them but ideally if like to be able to use it to check is com ports are active before I go and try to access a port that Is not online and have it error out my sketch... That would be a great thing to add to processing of it isn't here already

Hey I'm new here.
 I also have a problem with "Serial.list".

Applet starts up very slowly (30sec). It seems to be due to this code (1).

1.       for(int z = 0; z < Serial.list().length; z++){
           String pn = shortifyPortName(Serial.list()[z], 13);
             if (pn.length() > 0 )
             comListbox.addItem(pn, z); // addItem(name,value)
             {       
                 comListMax = z;
             }
         }      
   
2. String shortifyPortName(String portName, int maxlen) 
   {
   String shortName = portName;
   if(shortName.startsWith("/dev/")) shortName = shortName.substring(5); 
   if(shortName.startsWith("tty.")) shortName = shortName.substring(4); // get rid of leading tty. part of device name
   if(portName.length()>maxlen) shortName = shortName.substring(0,(maxlen-1)/2) + "~" +shortName.substring(shortName.length()-(maxlen-(maxlen-1)/2));
   if(shortName.startsWith("cu.")) shortName = "";// only collect the corresponding tty. devices
   text("InitSerial -  "+shortName, 300, 550);
   return shortName;
   }

Serial.list() is a slow operation, and you call it for each loop, twice since you also call it in the loop condition!
Assign the result of Serial.list() to an array before doing the loop, and use this array instead.