I was using a nice one but they stopped maintaining it and it never had the Combat Ability window added or any of the recent mods. Bear this in mind when looking at nice UIs. Unless you are into bending XML yourself.
EQInterface just posted a new range that does pretty much everything I want called Tablets. I'm gradually changing over to that on my chars. It is modular and fits together well.
I tried some of the more graphically adventurous ones like Steamworks and while pretty it took up way too much space and was downright dangerous. For example clicking anywhere on the spell bar (which was huge) except inside a gem opened the spellbook. Trying to cast a spell in combat and clicking a fraction off had you sitting down in front of the mob
Some others looked good but were fixed formats with only two chatboxes built into their "console".
Having spent a long time being "loyal" to the default interface I now feel deprived when I have to open inventory to click something or see my exp bar.