I didn't try KiCAD right away because I read lot of (apparently old, or FUDish) notes that it lacks basic features, unstable, and complicated. I finally got to try fairly recent version of KiCAD and was astonished how logical, fairly easy to use, and well-performing it is. Yes, it is still could do better, for example, it's hard to understand what precludes to use direct manipulation GUI, where you can drag an object with ... dragging an object with mouse, but at least commands for manipulation are standard, complete, and available via context menu. So, doubts off, KiCAD should be *the* toolkit for Open Hardware.
So, what are the outstanding features of KiCAD?
- Separation of schematic symbol vs PCB footprint - they are not linked in the component library, but instead are linked as part of PCB design process
- Text-based formats for all files
Of course, its standard library contains all/most discrete components. Next, for infinite number of ICs, you don't need to draw each of them in all possible and impossible packages - there's finite number of packages, KiCAD already has great selection of, and you can create missing once and reuse it for new chips very easily. Secondly, a schematic symbol for a chip is a rectangle with pins sticking out of it, so to "create" a new chip, only pin names needed, the rest can be easily scripted thanks to text-based format (and there're existing tools, albeit they don't seem to be open-source).
Now few notes about installing. Current version of Ubuntu ship rather old (one-year as of writing) version of KiCAD, only upcoming Quantal ships (as of now) 0.20120526+bzr3261-1, and that's what I downloaded and installed manually on Precise (12.04) without any issues. There's also daily builds from trunk, and that's what I'm going to try next, just wanted to start from a known stable reference. So far, I had one crash with 0.20120526+bzr3261-1, without any adverse effects.
Don't forget to install package kicad-doc-en. Unfortunately, Quantal's version still includes older version of tutorial, you need latest version called "Getting_Started_in_KiCad.pdf", you can find it here. Following the tutorial will give you complete walkthru of KiCAD workflow, enough to produce your boards, including custom components.