Seemed promising, but turns out to be irrelevant to me. If I ran Windows I could already run all those browsers. It would be really nice if they released a version that could run on OSX.
It's extremely helpful as a web designer to be able to check compatibility across all browsers without having to install them. Installing IE6/7/8 on the same machine is not recommended.
It might just be me but their processing times seem to have been growing and growing. Also I've been getting frequent erroring machine s(screenshots obscured by dialogs etc.). Might just be my luck though.