I didn't provide a status report for some time, so what happend in extended layout world?
I stopped to waste time with baseline alignment and switched to spreading natural size support over GTK+. As a result of this effort many widgets and one cell renderer are providing and interpreting natural size information now: GtkAlignment, GtkBin, GtkButton, GtkCellRendererText, GtkCellView, GtkFrame, GtkHBox, GtkLabel, GtkSocket, GtkTable and GtkVBox.
When working on GtkVBox and vertical natural size aware alignment in GtkTable I realized GtkLabel doesn't support ellipses when rotated. So I implemented ellipsizing support for rotated labels. This code only works properly for angles being multiples of 90° so far (first screencast), but I managed to write some test program getting ellipses right for any angle (second screencast) - just have to adopt the code to the label.
Completly unrelated Teemu Ikonen reminded me of my common file format chooser project. So I moved the code from Bugzilla to libegg. Finally I also figured out how to automatically integrate that widget with file choosers. So I added file filter synchronization and automatic file extension appending (third screencast). The code still is quite rough. Icons should be retrieved via the MIME type API of GVFS. Nevertheless it would be nice if interested parties would verify if it works for them in principle. Change requests should be posted in Bug 440431.