We need to support OS X because Apple has cast the dice already. It's the future of the platform. Without OS X, there is no Apple, there is no Macintosh.
I have never encountered anything like the instability issues some people report with OS X (I've managed to make it crash only twice since I loaded 10.0 on my iMac DV SE), but I'm sure some people are having problems. Those issues are being addressed as quickly as possible by Apple, but they need the assistance of Mac developers like -- QUARK.
It's a two way street. Quark helps the Mac platform succeed in the graphic design/ prepress market, but without the Mac, Quark wouldn't exist as a company or as a product. And let's face it, Quark has been resting on their laurels for a long time. They're coming out with an OS X native version some time around the end of 2002, which isn't exactly speedy development.
The other side of this issue is that while Quark users are a big part of the Mac market, Apple is trying to get out of that "Macs are for designers only" bind that has stymied growth of the Mac for years. Now here Apple is really putting out tremendous effort to move the platform forward and provide value to all of its existing customers (not to mention convert home and business users from Windows), and the graphic design and prepress community is loudly complaining about OS X.
I think that makes the Mac look like a platform beholden to a very specific niche market. Prepress folks are notoriously slow to adapt to change - witness how long it's taken InDesign to grab a foothold in the market. I understand the reasons why, but Apple has to do whatever it can to get developers on board with OS X. It's the only way to get the Mac out of the frustrating position it was in for years.
As a web developer I am thrilled with OS X. I can *finally* create all the content I want - text, video, audio, Flash, you name it , create the database, develop the scripts and apps, run Apache, test everything, and deploy *all on a Mac*. With OS 9 this simply wasn't possible.
It just seems like its in our best interest as Mac users to push on software developers as hard as possible to get those OS X apps out the door. The best way to do that is to dive in and embrace OS X.