Personally I feel the benefits of using a jo are that Aikido can be practiced
I agree, any excuse will do for me...
My teacher emphasizes a lot of very detailed stuff when we work with the jo.
What I find very helpful is the different ways of changing the distance to your partner by leading the jo in different ways.
But what I enjoy most is playing with the different levels in which one can turn or twist the jo (as a lever) easily without any force at all. That has also taught me a lot for te waza. The whole lever idea is pretty much missing when working with a sword (at least I believe so - please correct me if I am wrong, because we donīt work with the sword very often and I am not so familiar with it).
Distance and maai are apparent when working with the sword as well as when working with the jo, so thatīs not so different, I guess.