Weirdly enough, the iPad Mini is probably the iPad most used for work. The size & weight are perfect for many scenarios. Pilots, warehouses, and field work of all sorts.

For me personally, it's my travel machine. I've done all sorts of things with it on the road. From SSH to using Photoshop to make some last minute edits. It (barely) fits in my pockets so I don't even need a bag for it. Probably my favorite machine ever at least in terms of form factor.

Screen size does seem to be a personal choice. For me, I've always liked small screens for portability. I'm the weirdo who actually got work done on the first gen Asus EEE PC and didn't mind it. But I can understand that wouldn't be for everyone.