I use the HD version a lot. For iPad. If you have the retina version of iPad, it looks and works great. I can't speak for other versions of iPad or TapaTalk 2.
You can post from the app once you log in to the forum.
Look upper right corner to start a new thread. To quote a post, tap the post and a menu comes up with "Quote, Moderate, Copy, Share, Report, and Web View" choices. In the bottom right corner is a reply to thread button.
You have to log in to post, etc.
I spend enough time on the site, obviously, that the $4.99 was easily a worthwhile expense.