I think there's some of folk who will, just for Flash's new capabilities in 3D and the new smart tools in Photoshop. I've been very happily working in CS3 for a few years and have no need personally. Depends on your requirements I guess. In a web context I think the advances in Flash might be worth it, but the Apple/Adobe handbags has put a lot of people off and are waiting to see what transpires there.
If I had version 6/7/CS1/2 I might consider the move, otherwise it does seem like a huge expenditure.