My word this is big. At first sight it looks like a comedy iPad prop for the latest Dom Joly satire. When I say it's big I mean huge - the screen is effectively the size of two iPad Air 2 screens side by side. However it also feels very light, no problems with holding it in two hands. Balancing it in one might prove awkward though.
That screen is a typical Apple screen, which means bright and sharp. No sharper than other retina displays though, the larger size combined with extra pixels give the same PPI as the Air 2, slightly lower than the iPad Mini Retina.
Still it's a big screen. Did I mention it was massive?
Which is good for multitasking, but not so great for usability. It's an awkward machine to use as a tablet, controls on screen are a long way away and your hands have much further to move to activate them. Typing on the soft keyboard whilst holding it in your hands isn't the greatest input experience you'll ever have.
It feels like a machine designed to be used on a desk or lap. But then it doesn't have the controls to make that a comfortable exercise. It needs support for a mouse pointer at the very least.
Ultimately my initial impressions are that the Pro is a more compromised iPad than the Air, trading power and screen size for comfort and usability. It's best suited to use on a desk yet as a deskbound machine its less useful and less usable than a MacBook.
My only reservation is that I didn't get my hands on the Pencil. This might be the one device defining accessory that makes the iPad Pro a must-have machine for designers and artists.