Unfortunately it's kind of outdated and no manufacturer has taken up this unique form factor since the VAIO P. When they do, they are guaranteed to have my money.
For someone who heavily relies on keyboard use and mobility, I find it has upsides relatively to the tablet + keyboard cover in several ways. First, the specialized dimensions of the screen, chosen to match a decently sized keyboard, no more and no less. Second, the absence of a kickstand and the flexible rigidity of the keyboard/screen joint, making it a real "laptop": you can use it on your lap and on uneven surfaces.
For someone who heavily relies on keyboard use and mobility, I find it has upsides relatively to the tablet + keyboard cover in several ways. First, the specialized dimensions of the screen, chosen to match a decently sized keyboard, no more and no less. Second, the absence of a kickstand and the flexible rigidity of the keyboard/screen joint, making it a real "laptop": you can use it on your lap and on uneven surfaces.