Yeah they don't test CSS performance, which is where I think the majority of the performance gain comes from. It's impossible without a professional setup and some kind of application timer and browser debugger to verify the claims: a typical website can have several css files, a html file, several javascripts and dozens of images. It definately does seem quicker than IE7, similar to firefox, and slower than Opera. Sites like
http://news.bbc.co.uk are really fast (must be html heavy), sites like
http://zeldman.com (css heavy) are not as fast as the fastest competition), this on our work connection.
Rendering engine is great, mac on pc experience is great, native ui integration is poor, memory usage is 3x typical Opera, and it's a beta. A good first test I would say.