Nerd rage inc.^^
My main argument against the usage of this "HUD-style" is:
I want my UI to be fitting and looking "uniform". Having a HUD for target/player makes unitframes for player/target redundant/obsolete. But creating a HUD that is fitting "normal" unitframes (for party/raid/focus/mt) will at least be - difficult.
I can't see how a HUD would improve my tanking, since I have my player-/target-frame just in the scope (beneath my gnomish feet), so there's no benefit.
The benefit of my normal frames on the other hand is, that they match the rest of the UI.
I think it is a question of personal taste and nothing to argue about (Pixelfonts anyone?
).