As you can probably guess, the screen slides down so to covers the keyboard. With a 10 inch screen, the keyboard is probably the size of one you'd find on a netbook, but as you can see from the picture there is no track pad. That's one of the tradeoffs with this design, but it shouldn't be much of a problem. The screen is just inches from your fingertips.
It's shipping from Amazon with 16GB flash storage for $480 or 32GB for $580. Weight is around 2 pounds, which is no surprise given the keyboard and the complexity of the hardware design.
Now, while this design is new to Asus, it's not the first device to use this form factor. There are any number of phones that have a similar design, including the HTC Touch Pro 2 at left. There have even been a couple 7" models that look almost a junior version of the eeePad Slider (I can't recall the names, though). There are also a number of larger tablet hybrid models that commenters have pointed out over in this post.
But what sets the eeePad Slider apart from the earlier 7" the size. Those smaller models suffered from the same cramped conditions of 7" netbooks and that limited their usability. This device is priced to compete with but 10" netbooks and 10" premium tablets. I'd definitely get this hybrid over either a netbook or a tablet.