I do like the health bar the top of the tooltip. I don't think I've ever seen that done.
I don't like the little block in the bottom left. The micro menu isn't really useful, and the XP/rep bar would be better placed underneath the action bars in the middle.
The button border texture you're using (looks like the one from NeavUI) doesn't really match the other textures. Maybe look into creating your own button border, or try something like the
DaedUI Masque skin which has a more "Blizzard" look to it.
The round unit frame portraits and minimap seem out of place with the blocky shapes used elsewhere. If you don't want to create your own unit frame/minimap textures, try making the corners of the action bar block round, instead of flat cutoffs.
What is the floating "36.5%" text over on the right near the bottom?
Either get rid of the chat frame background, or make it more visible. Currently it's not solid enough to offer any increase in readability, but it's just visible enough to be annoying.
Finally, what is the purpose of the 5 big buttons above the action bars? They don't have any keybindings shown, but they appear to be action buttons, which can only lead me to conclude you
click on them (shudder)... if that's the case, you should really re-train yourself out of that habit.