The pre-beta is going awesome. I would say it is better then Vista itself so I have migrated over to this full time for most of my computing needs. I was able to activate it with an old beta key that Microsoft gave me back in 2006 when I first tested vista. I don't know if this is intended or maybe they just used the same key generator to issue out the new keys.
Either way, I am happy with the new changes but I cannot wait for Build 6933 with the new taskbar. I hear that they are going to open Beta mid december for some of us to give it a try.
The migration of Mesh works nicely with Windows 7 as well, I can't wait until they start to add the apps to it so we can test out those functuality as well. I am currently battling with an audio problem with my microphone as I want to post some camtasia videos on the forum for people to see.
I will let you all know when I get this sorted out.
Try to get a copy of it it's worth it.