Moi is probably most similar to Rhino, since Michael is the Father Of Rhino and Moi has most of the basic functionality of Rhino. The mesher is already better than Rhino's and I like Michael's guides better than Rhino's smartTrack. Moi is much more forgiving, too.
I haven't had much time to play with Moi lately, but I'm definitely planning on buying.
I'm really excited to see what Moi will turn into. I know if Michael Gibson is involved, it will be very cool.