it looks like the basic skin isn't all done, they kind of just pulled the menu all the way over the display picture and didn't even fix the items list so that it goes to the top too.

There is a big diffrence between transparancy in XP and Vista, in XP is just an alpha setting, nothing is splached out in the background like in vista.
if you are able to read text through a window it can be quit anoying, so I think thats the reason the dont have transparent windows in the basic skin, and because the full effect uses DirectX and if you dont have the graphics card for that stuff it will use alot of resources in software mode.

but the menu problem they should be able to fix Smiley