Much like Alex, both of our robots have had a rear wheel design that allows them to drive off wedges. It's a really useful feature, at least in our experience; it has saved us many times. Our current machine can be lifted at the front to beyond 45 degrees and the back wheels still keep in contact with the floor.

We do still see the sort of skirt approach in hinged scoops. They're not as popular over here as they are in the US, but even those, often way sturdier than typical skirts, get ripped off quite often.