I've been using Tapatalk 4 on Android since the beta version. It lets me keep up with the forum even better than in the browser, although I hate typing on the phone screen.
I'm annoyed that I had to pay even $.99 since I'd already bought v2, but it is worth it. It was confusing having both versions of 4 (beta and release) on my phone at once though. I had to uninstall both, then reinstall the release version to be sure I had the right one.