We've put some of the styling-related components online on http://appuicomponents.com/ but the layouting engine isn't there yet, I do feel it's valuable enough to productise eventually. The main problem is lack of polish right now. Interface Builder isn't much use once you get to that level of customisation - there's no way to set properties your subclasses introduce, let alone previewing the automatic layouting. I'd like to fix that at some point and have some ideas on how it could be done. Aside from that, I also still need to document the system, and tidy up the code implementing the layouting, as it's currently not the easiest to debug or find out why something isn't being laid out as you were expecting, even if the layout system itself isn't doing anything wrong.

Then of course there's the fact that I'm spending almost all my time on our startup, which is completely unrelated to iOS. (but it has a Cocoa-based Mac GUI, hence my recent Cocoa adventures)

Actually, if you're interested in the layout kit, go ahead and drop me a line (email on the website I mentioned, or in my HN profile) with what you're trying to do - if it does what you want, I'd be quite happy to progressively tidy it up and document it if I've got one or two users who are willing to put up with the rough edges initially, in exchange for some hand-holding.

Thanks for the link to Sensible. Are there any well-known apps using this stuff?