What else can you do with serial linked amiga's other than playing linked games?
Really, the parallel port is the more useful of the 2, faster transfers, sound samplers, MasPlayer (for Mp3s), video peripherals, etc. There was even an Oscilloscope app for it.
The only other use I can remember for the serial port aside from a null modem or a real modem was printing. I believe the OS came with several serial printer drivers. Of course, before high speed net, the serial port was THE way to download software and talk to other computers. I was still using a 56K modem on my A3000 for WWW until about 2008. Come to think about it, I did use the serial port to synchronize a Palm to my Amiga.