Tapatalk works well enough for what I use it for - the only things bothersome are the scripts not working and the way the sticky threads are presented separately (though the 'participated' feature is nice).
Usually connect over Wi-fi or 3G/4G, so speed isn't a problem unless I'm out in the countryside (where it's so slow as to be not worth the bother anyhow - for almost any site) - so I can always bring up the site in the browser if I really want to sign up for something before I get to a PC (just because you want to not forget it), but that would be unusual.
Given the numbers moving to mobile (myself I use my PC's a bit less then I used to) it may be worth the investment, if not now then later when more are accessing that way - as of now I think tapatalk is a good (if paid) solution.