On Google Play I see 100M+ downloads of the official Reddit app. 5M+ downloads of Reddit is Fun, 1M+ each for Boost, Bacon, Sync, and Relay. Many more in the 100K+ range. Thats maybe 10% at most.
I wonder how many power users, heavy users, or content generating users use unofficial apps. The passive lurkers are great for ad revenue, but the people who comment make the site worth browsing.