UI System for Non-minimal User Interfaces

NGUI is great for minimal user interfaces, huds, etc, but if your "game" turns into an "app" with many hundreds of UI elements in PSDs, each requiring pixel-perfect positioning to match the source art, it becomes really slow to build a feature.

Additionally, the sprite/texture distinction of NGUI becomes a pain when you're not actually that concerned about UI draw calls because, say, you've left your 3D world and are in a 2D mini-game scene.

We just can't get the efficiency of building complex UI in NGUI to match using other (non-Unity) systems. The best we've got is using FastGUI to export sprites from the PSD, then manually importing those into a master scene with behaviour attached to the buttons. We also have to handle large textures separarely.

Does anyone have a recommended system for non-trivial UI development, with good workflow from PSDs?

(None of this should be considered a knock on NGUI. We'll continue to use it for in-game UI, and for anything we've already built It does what it does well.)