So I read through all gazillion comments on ThemeLab's interview with the owner of Premium Mod.
As someone who has contemplated developing and releasing wp themes (for a cost or free), I have to say that this is a huge deterrent. Why would I put all my time and effort and love into something that can essentially be stolen. I know it's all cool under the GPL, but to me, I would feel robbed.
On the flip side -
We can talk about how GPL is ideal for the good of the wordpress community. So if a potential WP "themer" is thinking, "no way, not worth it" - it's not helping the community! I bet $100 that Woo folks and other "Premium" themers are right now contemplating the next step or move for their business since their model is now at risk. I don't think it will crumble in the near future, but it is pure logic. Why buy the cow when you can get the milk for free.
Speaking of the future, perhaps rather than worrying about improving the WP community, we should look at the overall design/development/web community. How do Premium Themes (GPL, free or paid) contribute to the community as a whole? Wordpress is not the end all, be all of the web. It's an awesome tool. I use it every day and develop all my clients sites with it. But it would be stupid to think that the web world stops at wordpress.
Also -
If your income and livelihood will be greatly affected (diminished) by the anonymous jerk who is behind Premium Mod, then you're not doing business right to begin with. See this as a path to grow, to develop, to learn, and to contribute to the web as a whole. You cannot base your entire business on developing premium wordpress themes. I am sorry, but it makes no sense. You go with the flow, you go where the web takes you.
My two cents, from my perspective, off the top of my head.