There's just a flurry of complaints about CS3 crashing under Yosemite. The upgrade is known to damage CS5 installs. Adobe only certifies CS6, CC, and CC 2014 as being tested for Yosemite.
I would not advise it. You would more than likely have to reinstall CS3 and its' updates, as well as your printer drivers and no guarantee it will be the same.
If your work depends on CS3 functioning, hold off for now, or until you upgrade Photoshop.
You are taking chances you probably don't need to. If it works, don't fix it.
Bad New, but thank you. Lloyd
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