I've recently given lectures on Red Hat Storage and GlusterFS at two hottest IT engineers' community events, #hbstudy (Heartbeats Study) on 2012/08/22 and #ljstudy (Linux women's study group) on 2012/07/25. I don't have an exact figure for the number of attendees, but the registration site indicates more than 100 attendees(!) for each event. Amazing! Japan might have the largest active/potential GlusterFS users.
One more cool thing is that Solution Architect from AWS-Japan (Katayama-san) gave a lecture on how GlusterFS fits in the AWS architecture and how it fills the current gap for the shared filesystem on EC2.
You can see tweets from people at #ljstudy (http://togetter.com/li/344979). As it's in Japanese, you may not understand what they are excited about, but I believe you could feel their excitement and serious interests especially in the technical aspects of GlusterFS. Questions from audience were mainly about the internal architecture of GlusterFS such as how replication xlator hits the balance between reliability and performance, how gsyncd is different from the bare rsync, etc... Yes, this is really the open source world. Sometime audience has much deeper insights than lecturers ;-)
Here's the links to some slides (in Japanese!) we used at the events.