My Feedback as a guild leader:
The good stuff. The new tab system is really nice. Makes things more organized. I like the new look as well, and the lock comments and hide thread functions. It is now much easier and more streamlined to create a guild wide message.
The bad stuff. I despise the fact the message center is now fullscreen on mobile. At least give us the option in settings to go back to window mode. The name and timestamp in bold at the beginning of ever message is distracting and obnoxious. It is ESPECIALLY obnoxious the timestamp that is basically now a part of every thread title, making all the headers harder to read.
Needs tweaking. The mark as important function ought to automatically stick a thread to the top of the page. If I'm marking something important, I want my guildies to SEE it. So it should be the first thing to show up when they open the guild message tab. "You can view important messages using the new filter system" you say? Sorry, but how likely are players to click through the filters every time they get on? I want even the LAZY guildies to see it.
The favorites function has a similar flaw. The concept of favorites is that they are messages you use a lot and want quick access to. Marking something as favorite should either move it near the top of the list or, my preference, the favorites "tag" should have ALL your favorite threads from BOTH categories, guild and social, rather than having a separate favorites section for each tab.
Thanks for the update and the new features! It came with a few kinks but I like the concept and think we're headed the right direction!