Being predominantly lesbian, I find that one of the biggest issues I find while reading a lot of Yuri/lesbian porn/whatnot is the abundance of fake cock. Yes, fucking is hot, however, statistically most women do not come from penetration, or at least penetration alone.
Oh, and g-spot orgasms do not happen spontaneously.
Beyond that, Yuri tends to require females to take a more active role in sex beyond just laying back and getting fucked. One or both women must actively desire to go into it to pleasure her partner, stepping out of the submissive role.
Also, girls tend to be a lot more emotional in general than their male counterparts. And twice the female equals twice the PMS....