Very very nice! Thank you for the great client. Many things are done exactly how I also would want them to be done. You have a good vision. I post here my thoughts about areas of improvements. They are just my opinions, and perhaps some or most of them are not what most people want, but just laying them down in case.
Main room:
- version number maybe into some corner or somewhere. Now when, thanks to Zerokun!, it is easier for a layman to try the client, it could be easier to keep track for everyone when reporting bugs or feature requests maybe.
- The tab list for rooms could stay maximized when I click another room to open it. Now it doesn't matter whether I have it maximized or minimized, when I switch rooms, it will go to 'minimized' view.
- The tab list is not showing all rooms I have open (even when maximized), when I zoom in the page (or lower resolution). It shows some 11 first ones on the list. This problem probably concerns only those that have a lot of rooms open. I have 23 rooms. You have already added a neat feature to organize the rooms by allowing to move the room to the top of the list, which would help me by moving the more important to the top, but this behaviour doesnt persist when re-login.
- The games list and the chatrooms are currently divided horizontally with around 50/50 ratio. Would be nice to optionally be able to resize the ratio. I am thinking of seeing 2/3 or 3/4 of screen being occupied by the chatrooms, and only small portion visible for the running games.
- Personally I like this approach of showing the 'active games' and the chatrooms in the same view, rather than like in the original kgs where you see the chatroom, and the games played in that chatroom in one view. I bet someone though would want to filter only games played in some certain room. I am thinking of some filter text field on the "Room" tab, where you could type in text and it would filter games from rooms that match the text. Maybe it's useless, I don't know. At least I prefer this choice of chatroom + active games in same view!
- games' time settings on the active games list, like in cgoban-h. Sometimes when you want to observe a slower game, you wouldn't need to open the game and see their time settings, but instead see it on the games list already.
The game window:
Must start by saying that playing out sequences or using editing tools while observing a game by simply just playing out moves or edits is just fantastic!! Simple idea and it just works. Also very easy to jump to the actual game line by clicking the tree view.
- I would like to be able to view the list of users who are observing the game. I can't seem to find the list anywhere. If not done yet, I guess it is going to be done conventionally by adding another column to the rightside of the chat area? Anyway, keeping it optional to toggle the users list on and off would be nice too.
- About the black top bar visible in main room and game window:
In the game window during own games (when they're added), when you play with a small device, every millimeter counts towards convenience. Currently the black bar is restricting the maximum height of the board a little bit, so if there was a button that you could use to hide the top bar and give the maximum possible size for the board, it would be nice.
player info:
- The feature in original kgs client, where you can browse the game history of a user through their user info page is quite nice. I can see that you are listing the most recent games with either W or L, which is nice, but not as informative as with the original client. I am all for the philosophy for not adding features that will create unnecessary bulkiness, but I think here some more convenience wouldn't hurt. Maybe you just yet had not got to that part to add this feature, but if it is becoming too heavy with it, maybe add another button inside the user info popup that loads another popup listing the game history, or just simply a hyperlink to a users kgs archive page, eg.
https://www.gokgs.com/gameArchives.jsp?user=thecaptainBulkiness:
- On my rather low end pc, opening multiple games simultaneously, there is a slight lag when switching between games. It is still usable, but the memory footprint is ~400M with 3 open games. In OGS, 3 open games and the chatroom in 4 separate tabs consumes total of ~300M. The kgsleben browser with observing 3 running games starts with around 75M, but after 5 minutes it is at 100M. However kgsleben seems less polished at this point, so maybe their mem footprint will be on the rise aswell.
Internal error: Check webapp logs:
- Zerokun, I got logged out and had that message. Guess there's nothing I can do to help debug it.
and 
? ( Not 3D, not "fake" clamshell grains )