I have used the R320 with the Fanatec endurance button module for over a week and it's indeed a great wheel rim! The grip is perfect for someone like me with small hands, with or without gloves. With bare hands the material feels really nice, not too rough or sticky. The best part aside from quality and everything is that it doesn't block any view so I can see the dashboard better!
I do have one little complaint though: because its upper half is completely open, when turning the wheel, one of my hands has to solely rely on the grip strength, whereas with other GT/formula wheels such as the Fanatec Formula V2.5, I can use the outer side of my thumb to push the wheel. I didn't even realize this until I started using R320. I was using the Fanatec Porsche rim, and I could use my ring finger to push the wheel as it rests just under the joint, which is not possible with R320 because the grip diameter is way larger. After about ten days of using it, my grip strength has certainly improved but it's still somewhat tiring.