This app has pretty much grown to be the de facto method for forums to add mobile support, so much so that I can't recall forums ever going through the same explosion in apps that blogs have in the past few years. It did take MR a while to join the party, and Alex, the owner of MobileRead, had considered adding support for Tapatalk a couple times but held off for one reason or another. This would have required installing a plugin, and as I understand it the plugin raised security and technical problems that Alex wanted to see addressed before he installed the plugin.
Given that MR also had a mobile site at mobileread.mobi, we thought there was no need to rush the issue.
I'm told the app works well, though I have not tried it myself. The app costs 3 bucks, and I don't feel it's worth it. I don't tend to browse MR while mobile and I don't see that changing any time soon. I'm also balking at the thought that I would have to buy an app for iOS as well as Android (I do have an iPad); as a matter of principle I object to having to buy content 2 and 3 times.
You can find the Tapatalk apps in iTunes, Google Play, SlideMe, and for the BlackBerry.