I recently received the Ostrich Eggbot upgrade as a gift and have been enjoying printing on glass ball ornaments again this year. The larger chassis allows for printing on larger spheroids and the spring loaded egg coupler has an improved grip over the older version.
I later purchased an engraving tool which replaces the pen, but have had difficulty getting good contrast on clear glass ornaments. I'll continue trying slower speeds, increasing the number of passes, and try different materials for better results. Results forthcoming!