Actually, Diamond tended to make good products, and their drivers were actually pretty good.
I think your complaint is geared more towards the frequency with which they updated their drivers, which was almost never. When the drivers were released, they were usually pretty fast. Unfortunately, they never updated them to perform on par with the updated drivers from other manufacturers.
Good quality drivers for good quality products that were never updated. The lack of updates was what seperated them from the "good" manufacturers, and what eventually led to their downfall.
I still have a Diamond Stealth 3D 2000 working in an NT Server/Linux box. Never a problem with it yet, and it's survived through my P100, K6-233, and Celeron 300 before finally settling in the server.
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I am Jack's raging inflamed colon. Jack applies ointment daily to supress my fury.