It's always interesting to me to try to understand what makes someone 'fun' to work with. Some beginners are really fun and some more advanced students are just no fun at all.
Of course, you learn from the fun and from the unfun, too. A lot, also, probably has to do with moods and your own needs each day. Some days, I'm in the mood to move and roll and flow. Those days, beginners don't 'do it' for me.
I find that the most challenging thing about working with beginners is finding out how to get them to commit to the attack and stay connected without explicitly telling them, 'commit to the attack and stay connected.' I learn a lot from figuring out how to create this connection with someone who does not know what it feels like.