For the best XDA experience on mobile, try XDA Labs, now in beta: http://xda.tv/labs

*Please clear app data after installing v4.0.x if you encounter login issue (settings>apps>xda premium>clear data)*

This app lets you access the world-famous XDA forums, plus reply to threads, add new ones, manage your PMs, and more!

The premium XDA app is ad-free and has additional features versus the free XDA app.

Please note: XDA Premium works best over WiFi or high speed cellular data. The first load might take the longest even if you're on WiFi.
From version XDA Premium 5.0.22:
3/31/16:
Design tweaks and bug fixes. For the best XDA experience on mobile, get XDA Labs, an app built entirely in-house. It's ad-free, fast, and fully Material Design! Go to xda.tv/labs
All versions
April 1, 2016