The Toshiba Libretto W100 is equipped with a dedicated keyboard button that provides quick access to the device's preloaded on-screen keyboards. They can also be launched by tapping an icon in the toolbar at the bottom of the screen, but I find the hardware button to be more useful since it's always within reach.
However you choose to launch them, the keyboards appear on screen almost immediately and are instantly responsive. They can be used on either screen and sit on top of whatever is being displayed.
There are six different layouts that you can switch between using the toolbar above the keyboard; each offers haptic and audio feedback as well as StickyKeys functionality. You can choose the order that the keyboards are shown when you tap on the switcher icon, completely hide the ones you don't want, and decide whether you want the last layout you used to appear the next time you launch the keyboard. There are also dedicated cut, copy, and paste functions in the toolbar.
Some keyboards work better than others in some situations, but switching between them is so fast and convenient (especially since you can customize the order) that I don't think it's vital to really become proficient with any one layout in particular. I've been switching between two or three, depending on what I'm doing and how I'm using the W100 (on a table or between my hands), and am doing fine.
The Libretto's 7-inch screen makes touch typing difficult, but multi-finger typing on the full-size layouts works fairly well and thumb typing on the split keyboards is even better. Even on the six-row keyboard, the keys are still big enough for pretty accurate input.
Responsiveness is better than any other Windows soft keyboard I've used throughout the years, but it's still a tiny step behind what you'll find on mobile operating systems like Android and iOS because you need to be a little more deliberate in your taps. There are some other things that could be improved but before I go into that, here's a look at all of the layouts:
Other improvements I would like to see are adjustable opacity, automatic keyboard launch when tapping in a text field, and an automatic minimization when tapping the underlying window/screen.
If you need to do extensive typing, a Bluetooth keyboard is a better choice. But for everything else, I think the built-in virtual keyboards are up for the task.