It all depends on the meaning of "serious".
All i know is that i became a better teacher after i learned (Thanks Messisco sensei!) not to take myself too seriously.
I usually have an concept of what i believe my group should work, and shape it according to who shows up.
I emphasize variations of ikkyo, shiho/kote and irimi/kokyu, which i view , together with koshi nage, as Aikido's whole curriculum (personal opinion guys!).
I personally try as much as possible to make sure my friends/students are not "falling" for me, but being actually unbalanced by my center and have no distress in exposing myself as limited.
I do my best to get all questions answered or at least provide the means for my students to make a research of their own.
I do my best to participate in other sensei's classes as student so as not to lose my "beginner's mind".
How serious am i as a teacher? Not enough to waste a good joke