I had the guys up there at Rotovac do some repairs on my 360i and when I was there I asked them about a 12" brush head with Teflon glides. They built one for me and now I have a few jobs under my belt with it.
I really like the extra agitation it provides on heavily soiled carpets. I also really liked how gentle the head is close to wood and tile transitions.
One thing I noticed that I wasn't super excited about... The brush bristles seemed to hinder the jet fan pattern on the outer edges of the head. In fact it I felt like the cleaning path actually became slightly narrower on heavily soiled carpets. I had to do closer overlap strokes than I used to have to do. It still cleaned really well though and am still happy with my purchase.
I decided to experiment with cutting a few rows of bristles around the jets. Kinda opening up the bristles so the fan pattern can still get closer to the edges