  We argue that a key challenge in enabling usable and useful interactive task
learning for intelligent agents is to facilitate effective Human-AI
collaboration. We reflect on our past 5 years of efforts on designing,
developing and studying the SUGILITE system, discuss the issues on
incorporating recent advances in AI with HCI principles in mixed-initiative
interactions and multi-modal interactions, and summarize the lessons we
learned. Lastly, we identify several challenges and opportunities, and describe
our ongoing work
