It works flawlessly! Here's a helper function for chatting which includes your handle before each message (helps keep track of who's saying what):

  KBUSER=`keybase status | grep Username | awk '{print $NF}'`;
  function say() { echo "$KBUSER: $@" >> /keybase/private/shared,folder,between,multiple,users/chat.txt }

Note: I made KBUSER a variable because `keybase status` takes about a second to run.