I'm an administrator at
fjrforum.com with about 10,000 members and looked at instituting Tapatalk.
No way!
Didn't like the way they embedded themselves into the securest parts of the forum software ( potential security issue), required regular updates (more administrator work and another potential security issue), and added hassle of potential expected support for Tapatalk. I've found this and other forums come up great on iPhones & Androids great natively in various browsers just fine!
I also have found extensive conversations on a forum for forum admins with concerns about the product including delayed-patch security issues, scope-creep, and troubling activity on the server side.