I don't know how common these use cases are, but I find touch support useful while doing some web dev stuff. For instance, in Chrome, pinch to zoom is more precise than ctrl-scroll / ctrl-+. It preserves the existing screen dimensions (ctrl-scroll / ctrl-+ makes the actual font size larger and alters dimensions).

I'm not so vision impaired that I need to do this on a day-to-day basis, but it's great for zooming in to see if I need to adjust a CSS border by 1px or something.

I haven't tested this thoroughly but I believe Chrome also supports the same set of touch events it does on Android. So if you want to make sure the mobile version of your site is touch-friendly, having a touch screen is less clunky than trying to emulate it with a mouse.

The use case that matters for me is: when I'm using them as laptops. Most of the time, my Windows laptops are connected like desktop machines: external monitors, mouse, keyboard. When I take my devices off the desk and go to a cafe or my living room, I use the touchscreen all the time. I don't reach for my mouse to click a button when I have a finger to do it. I probably don't go more than two minutes without touching the screen in that scenario, even while writing code. Scroll up/down is much easier with a finger. Pinch-to-zoom is obviously easier.

I have little experience with vertical touchscreens. Some friends cheap PCs and my tablet attached to a Bluetooth keyboard.

I discovered that I was naturally touching the buttons in dialogs and web pages and the checkboxes and radio buttons in forms. It's faster than reaching for the mouse or the trackpad. With the trablet it was the only way and it was good. No gorilla arm.

Touching links in browser can be fast too, but the target must be big enough. HN is particularly bad at that.

Basically everything that is easy to do with the touchscreen of a phone and a tablet is easy also with the screen of a laptop. But the screen must not move when you touch it.