Greetings obfsbridge operators,
tl;dr, you might want to upgrade your tor to the latest git master.
Trac tickets #4773 and #5040 have been merged to tor's git repository. This means that if you run the current git master, your obfsbridge will produce interesting statistics.
Specifically, your bridge will count the number of its unique users like normal bridges do (but because of some complications it was not so easy for obfsbridges). It will also count the number of users per transport.
Your bridge will then send these statistics to the bridge authority, and they will be published in metrics.torproject.org so that we can easily track the deployment of pluggable transports. You can experience the stats yourself by peaking at $DataDirectory/stats/bridge-stats.
BTW, make sure that you are using the latest obfsproxy written in Python, and not the obsolete obfsproxy written in C.
Cheers!