I use it, but only when I am away from the computer and haven't checked in for a while.
It annoys me mostly, for two reasons.
1. Threads I know I have already read most of, whether on Tapatalk or on the computer, it makes me start reading again from the beginning. More accurate sync between the two would be nice, but is it even possible?
2. When displaying unread posts on the computer, I go subforum by subforum, but Tapatalk gives them to me all mixed up (probably in date order, but that is irrelevant to me). Unread posts grouped by subforum would be better.
3. The unread tab (on iOS) is right under the "back to list of fora" button, and my fat fingers often hit the "back to list of fora" button instead of the unread tab.
Ok, three reasons then.
But is sure beats trying to use a mobile browser on a 4" screen!