After a 30 day evaluation, I purchased the Professional version
Architect today. It seems to be a pretty easy to use UML
diagramming tool and, best of all, sold at a very reasonable price
(desktop version is US$95, professional version is US$149).
I plumped for the Professional version in the end because it
includes code reading and writing. I sort of shy away from such
things – I prefer to use UML for the design and then let people
make their own way through writing the code – but I
figured it might come in useful in future and this version was
still well within my budget.