Anything that is of personal use is fine...and going by that, only scrolling combat text for your character (not watching others dps in your combat text).
So if one of your party starts hitting a mob, he will see his combat text, but you will not see his.
The buff/debuff tracker on self is iffy..... should you really see the debuff someone puts on you and/or its time limit? I wouldn't mind too much about someone seeing that they have a debuff on them via an icon or some such, but I don;t think the time limit should be seen. Its an unknown to you & should remain such.
The buff/debuff tracker on an enemy comes under "monitoring other players" and is definitley going too far. You should not know what buffs/ debuffs they have at all. Whether you apply a debuff or someone else applies it...it should never make anyone but that person aware that there is a debuff (if at all), and definitely no timers.
Addons I look forward to are cosmetic changes to the HUD, ability to move them, differing displays maps, mail and all other existing UI elements, although there is no guarantee I will stray from the minimalist UI as is...I like it atm. But maybe a future change with some nice designs? Ability to manipulate the group UI, cosmetic & movement.