Why is it a niche gadget? Basically a Tablet laptop is a more expensive Laptop that adds touchscreen capabilities for user input. But now let's take this matter in detail and compare a laptop and a touch screen tablet with the same specs like they were build by the same manufacturer and the only difference comes from the touch screen part.
Main differences between a touch enabler notebook PC and a normal laptop:
- Screen: it's thicker on a Tablet PC because of the additional layer (capacitive or resistive) and the electronics that control it and determine the user input precise location. Additionally the screen can pivot 180 degrees to allow a more comfortable use folded over the keyboard
- Stylus: a Touch tablet features a pretty big display, but precise actions from the user need a stylus, especially in applications like Adobe Photoshop
- Battery life: as touch screen tablets have more components than other laptops (the touch enabling layer over the display for example) the power consumption is slightly higher than on normal laptops so expect a shorter battery life away from the socket
- Software: this is maybe the biggest difference, as without proper software and programs to take good use of the touch capabilities of a Tablet PC there isn't much to do with one. This is also what Tablet PCs lack right now but maybe manufacturers will understand this and will try and offer customized apps for touch input.