It's a great device for professional users (or will be, which I'll get into below), but I wouldn't dare call it an iPad killer. See, the iPad and Mini are nearly perfect for what they do. They're media consumption devices with some capabilities for light workloads. I can't think of any one machine that does this job better than they do (well, besides the Android tablets, but I ain't about to get into that argument).
...the problem here is some people seem to be under the impression that this is all a tablet should be. That the iPad is perfect, and anything that tries to do more is instantly flawed right out of the gate because...hey, the iPad is perfect. If it were a good idea, the iPad would already be doing it. This is what I and quite a few other people here take issue with.
Take what ri0ku said above. Mudbox (Zbrush is better FYI
), Photoshop, Maya, Modo, Max. These are all programs that are meant to be used with a stylus against a screen. Drawing tablets? Mice? They're all surrogates meant to get us by until the day of the onscreen digitizer finally comes. This is what the Surface Pro is ultimately meant for. While it doesn't succeed flat out just yet, it's a great first step in the right direction. When they start catching on, you'll eventually see other programs start taking advantage of touchscreen UIs.
Right now, the one biggest thing keeping us from this glorious day are the UIs for these programs, and the OSes capable of handling them. Contrary to what people say, Win8 isn't a too-much-tablet-for-a-desktop OS. It's 99% a desktop OS with some touchscreen niceties thrown in as a half step towards...whatever. The same thing applies to Photoshop, Zbrush, and the rest. They're programs best used with a stylus against the screen, but the UIs are still very much meant to be used with a mouse on a large screen. PS in particular has tons upon tons upon tons of tiny little icons that look fine on a 15+ inch screen, but would be very difficult to see and hit on a 10.1 inch touchscreen. The same applies to Win8 in general. Yeah, it's got some tablet stuff in there, but the desktop is still a desktop. It's better with a mouse on a larger screen.
This is where the Surface fails in my opinion. It's a great machine, but the UI lets it down. Yeah, it's an Ultrabook in a tablet format, but it's still in a tablet format. Slapping a keyboard and mouse on it kinda defeats the purpose of what it ultimately is. It needs a UI to go along with that snazzy hardware and design. A UI it currently doesn't have. If you have to set it up like an Ultrabook to use it comfortably, you might as well buy an Ultrabook. The Lenovo Yoga and its ilk are much better Win8 machines than the Surface currently is.
The good news is if Windows 9 comes out with a much better touch-centric UI for the desktop, then the Surface becomes that much better of a machine the instant it comes out. The bad news is it isn't there right at this moment. It's great for the potential, that first step towards something a little more complete, but it isn't an absolutely must have machine as it exists right now.
The entire idea of a touch-centric tablet PC capable of everything a traditional desktop/laptop does isn't a bad idea. It just needs more work before it gets there.
