One example was the Vision modes, which got some attention lately and finally improvements happen.
Now i'd like to bring forth another topic, the HUD.
I'm not talking about the HUD bugs as they are numerous and obvious.
What i'm talking about is the design problems with it's coloration and layout in general.
Color problem:
The current MWO HUD uses yellow and orange color as it's base, which wouldn't be a problem in a game without orange and brown maps. On Caustic Valley there are situations when vital parts of the HUD (for example the cross-hair) are almost invisible.
Layout problem:
Now this is a huge one and it is very problematic. Fighting uphill or downhill is one great example for the issues with it. When one tries to fight downhill the arm crosshairs get obscured by the map tool, fighting uphill is a bit better, yet there are still some issues with the timer and the capture indicators getting over the target. The HUD tries to center itself on the crosshairs, this is why the marked part of the HUD should've been left clear for crosshair movement. One can test this issue on any map, but Alpine is the best example.

Another layout problem is the small and almost invisible Weapon group status indicator near the crosshairs, their small size and color makes them useless and they are tied to the HUD not one of the crosshairs which reduces their effectiveness even more so. If they'd work properly we wouldn't need an overly large detailed weapon list at the bottom right "corner".
Paper dolls are also wierdly placed, in a fight one thing a player should always be aware of is the status of his/her mech but it is almost as important to know the enemy mech's damage to compare these as fast as possible to decide if the fight or duel is going to his/her favor or not. Yet these parts are in opposite corners.
General unfinished feeling:
Then there are parts which shout that the product is not finished. A great example for this is the line connecting the arm and the torso crosshairs.
Considering this is the part of the game which is always visible to the player (aside from the occasional no hud bug), improving it should be a priority.