As more of a general comment, I'll be really disappointed if this is what 10.5 ends up looking like. It seems like more of a step-back in the eye candy department, especially when compared to Vista. I know that its still more functional and useful than Vista, but I was really hoping for built-in virtualization and transparency, and based on Looprumors, Apple Insider, and this video, it looks like none of this will happen. All of these features would be necessary for Mac to really become a legitimate alternative to Windows in the eye of the public.
I recently switched, with a 17" MBP, and I couldn't be happier. Almost everyone I talk to who asks me about buying a new PC, I recommend a Mac to, and if 10.5 supported virtualization and had transparency, Vista and the Windows platform would become basically irrelavent and I think you would see people switching in droves.
Hopefully this is fake, or at least just intended to show off tabs in finder. If one of the top 3 advancements in 10.5 come September is still just tabs in the finder window, I'm not sure OS X can still keep claiming to be far in advance of Vista once it comes out.