I too had some problems with releases prior to 9.0.4, but once I updated (knock on wood) to that release, we have not experienced "too many" problems...
One thing of note... I was probably amongst some of the earliest updaters to Mac OS 9.1, and was proud to do so... Maybe a little too proud, as this led to MANY, MANY problems, as soon as I attempted to utilize the newest OS, various apps - most notably Vectorworks (8.5.2.) and its associated programs...
Upon giving OS 9.1 the usual new OS "benefit of the doubt" couple weeks, and coming to a near paranoid shutdown, I have since removed OS 9.1 from all my "productive" machines, and have since not had "too many" problems, freezes, etc...
I am looking forward to the upcoming carbonized version of Vectorworks 9, but with the need to turn a buck with both my computers and its applications, namely Vectorwork Architect and Renderworks, I will tread softly, most likely on a "spare" computer, until I am as much certain that OS X and Nemetscheks latest VW release will work both reliably and productively...
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C M Harada
Perspectives Design
Group, ink
Denver, CO