I like it; I think it's functional and well-placed for the most part.
I would, however, reconsider the location of your unit frames. Perhaps putting them closer to the center of the screen would be better (or closer to your main area of focus). That way you don't have to look away from important stuff =)
Yeah, scale stuff down. And then you can probably hide some of your bars, some of them look like they don't need to be shown. The ones with cooldowns you should/can keep visible, however.
Looks good, but as said before Unit frames can be made smaller and placed more in the middle. And personally I like everything to be under a certain line (think everything under 1/3 of my screen).
In my opinion, the chat takes up waaaaay too much space. Download Prat and scale it down and remove the scrolling buttons, it's not like anyone use them if they have Prat ;P
Elsewise, I like the UI. Rather decent.
I like it, tho i dont know if your grids position is so good, its in the middle of the screen, and if you sometimes zoom in when you raid, you probably will have a hard time finding the void zones, and other things you have to move out of
my opinion:
first sight.. its nothing special but ok. u are a healer.. and therefore i would recommend u to remove spacings between the grid cells... and may your unitframes (player,taget,target-target) can be adjusted better in some way.. because your general focus (of your eyes) is @grid... and your playerframes are at the top... annoying to me.
furthermore your bars include homestone etc. and they shouldnt be in the middle of your mainly stressed skills... may u move them to the edge somehow... of course its up to u but may it gets more clearly arranged.