I've tried to use KnockOut 2 as a PS CS plugin, but find it won't add to selection beyond a certain point - which is INCREDIBLY frustrating, and a total waste of time. I asked for support on several occasions, and after waiting a week (as opposed to their 1 business day claim), got this response, and they marked my support issue as 'Solved'. I'm now after a refund as it's not fit for the purpose it was sold.

Corel has received sporadic reports of a functionality issue with KnockOut 2.0 while running on MAC OS 10.4. Our investigation indicates that the issue may be specific to certain hardware/software configurations, however the problem is not reproducible in testing. There is currently no technical workaround to resolve this issue, however our technical support department continues to investigate the phenomenon. When a resolution becomes available, Corel will publish a relevant document in our online knowledgebase (http://support.corel.com).