At my dojo, Penny Bernath teaches and I really do enjoy her classes. She does a great job of emphasizing fluidity of movement and diversity and variations of techniques.
I feel much like Tonya does about the "women only classes" question. It more of a matter of just seeing another woman there knowing that if she can reach the level of 5th dan (Penny) or even shodan, you can, too.
Lorriane DiAnne is Shihan, but I'm not sure if that's through Chiba Sensei's Birankai organization or with the Aikikai Hombu. Either way, she has incredibly powerful and centered technique.
I just wanted to add that sometimes being the only woman in the dojo can get lonely sometimes. It's not always a big deal for most women, but sometimes you just don't get the comaraderie with other women that the guys get with each other because simply there is no other woman there. I'm not the only woman in the dojo, but I've made an effort to introduce all the women to each other, now, there is that feeling and "us gals" can even have "locker room talk"
This is no call for women only classes but sometimes we are the majority or at least a significant minority in class.