Thanks for posting Ishmaru & Idanwin. I think Ishmaru's suggestions will be addressed with the new GUI that hailstone is working on.
As far as the HP/mana bar, I like the basic idea, but I have other issues with it and the current implementation. If you're standing on an incline, you'll notice that part of the circle will be non-visible because it overlaps with the ground. If we used the declining ring idea with the current rendering mechanism, it could render the relevant portion of the HP or mana bar invisible due to this problem. I'm considering an approach similar to shadows where the ring paints onto the landscape if it's below ground in any given place (basically, an inverse of how shadows are drawn, because we're going up instead of down) as a means to make visible portions of this ring that become invisible due to this problem. This would make Idanwin's idea feasible as well. Either way, I don't have a serious problem with the current ring, maybe in the future a config option can specify how HPs, mana and locally stored resources can be displayed (or if they are displayed at all). Perhaps another solution to make Idanwin's idea work is to always have the start/end of the ring facing the camera.
One thing that's on the 0.3 agenda is adding lines to the selection icons that show the health of each unit you have selected (along with being able to select more than 16 units at once).