I've been playing about with Magritte a bit more over the past couple of days, and I'm beginning to get a better understanding of it - I can build edit-forms and reports now. I can't quite see how readonly views work, but I'm sure I'll crack it eventually...
More impressive (to me anyway) is that I've found a couple of bugs in Squeak!
The Traits-Tests suite of tests leaves lots of classes like anObsoleteClassC3 hanging around very reluctant to leave again. I raised this on the squeak-dev list and was advised to raise it on Mantis (bug reporting tool). So my first Squeak bug has now been created.
I uncovered this issue because the Refactoring Browser started generating messages telling me that "AnObsoleteC3 class does not understand #directlyDefinesMethod". As I wasn't able to solve the underlying problem I fixed the symptoms instead, by amending the RB to ignore obsolete classes. I don't know how useful a fix this is, as the obsolete classes shouldn't be hanging around in such an offensive way, but it's my first Squeak bug-fix, and is now part of the RB codebase.