Tapatalk works well but there's been some security issues/bugs they've had that seem to be recurrent and a lot of advertising. Apparently not really responsive to feedback either. If you have a good mobile or responsive theme I'd say you don't need Tapatalk.
Mostly, the ability to have more than one forum in the same app (instead of an app for each forum). If you only visit iPF, then it would mostly be a matter of how much you like the interface compared to the official app. 😉 I think Tapatalk is a good idea for you ^^
I think you're better off using a resolution friendly/mobile theme on your board then using a third party app. That way you can still control the look of your site and not rely on another developer to keep things running.
Tapatalk has had some pretty big security issues in the past sadly, and that is why I'd never recommend them. Although it helps out, if you have your own forum's website being super responsive then it all should work out even better.
Or just make your own app for phones and be super elite as barely anyone has any for their communities what so ever.
I've heard nothing but terrible things about Tapatalk. While I don't have much experience with it, nor have I used it first hand, I probably would not be interested in using it at all.
I'd honestly steer well clear of Tapatalk. Its security history isn't the best as others have said and it has limited features compared to using a fully responsive site via browser 😉
I've pressed the Cancel or No button (can't remember what it is) on the Tapatalk popup at least 1,000 times by now. Tapatalk just doesn't seem to be useful for me.
It's a trade-off. On one hand, you make some users happy (a lot of people will request Tapatalk on any semi-large forum), and on the other hand, you sign up with a company that has a sketchy security track record.