urlwolf: Webkit is just the rendering engine that powers Safari, so the UI is not what is being tested (it will use the Safari UI you have installed and just swap the engine out). The rendering engine itself works fine on Windows (it doesn't suck, but remember it is a nightly, so every day may give you a new surprise!), slightly slower on the same machine than the OS X version, but still much faster than firefox for just about every rendering test you can imagine, sometimes by an order of magnitude. If you hate Safari for Windows period, then Webkit will look *idential*, it will just offer you all the new rendering goodies they are introducing...
Gecko is showing its age, and I'm hugely skeptical that Mozilla can get its performance anywhere near Webkit and Presto for their mobile project. But as embedded processors get faster, they can hopefull stay still long enough to let the hardware catch up (as happened when Mozilla first emerged all those years ago).