I've tried achacha and it was really good. I've been discouraged from growing it due to the slow growth. I haven't tasted madruno yet.
I would like to try madruno,lucs, and imbe - hopefully I can find someone to ship me fruit or stop by someone's place this summer.
To be honest, I really like the flavor of g.brasiliensis (lemon drop and superior lemon drop) and wouldn't mind just growing those, but again there is barely any edible flesh. They are probably the best bet growing up north.
My slowest growing tree is Madruno (same size with two leaves for two years) I only have one so don't take my word for it, second slowest is probably Luc. I grow Magonstana, Achacha, Luc, Madruno, Jorco, Lemon Drop, S.Lemon Drop, Livingstonie , Dulcis, Gerrardii, Gardneriana, and seashores. The fastest growers appear to be seashores, and Gardneriana, followed by Achacha, Lemon Drop, and, Livingstonie. Livingstonie, seashore, and achacha, in my experience have been better root stock than Lemon Drop.
I have had success grafting Prainiana on Livingstonie and on seashores.
Seashores, Prinaina and probably few others like dulcis are dioecious , you will occasionally hear from someone who has a strain that is self fruiting.