I wouldn't mind landing in a ball pit before boarding the metro...as long as what happens in children's ball pits doesn't happen with the Metro's.
I would like to think the writer meant to suggest ramps like those at major sports arenas that wind back and forth for a while. I think the slide/ramp idea won't work because of space issues and the fact that stairs/escalators are quicker for those that can take advantage of them. Nevertheless, I wouldn't mind having the writer's idea of slides implemented when going down to the tracks. I'm not talking about arena ramps (as she may have). I'm talking about those great slides we used to ride at the playground. Some slides could go in spirals to control the speed. Otherwise, a direct slide at my favorite Rosslyn station would cause people to reach terminal velocity before even making it to the platform.
Now that's what I'm talking about!
Maybe a direct slide would be a viable option if you're really in a rush - you'd just finish your slide in a big ball pit like at Chuck E. Cheese. If you're worried about getting your suit dirty from the slide, you could grab a specially designed cloth that not only protects you from the slide, akin to toilet seat covers, but also decreases your friction to gain more speed. I actually think the downhill-only slides would work. I guess I do agree with the writer's suggestion of Metro slides afterall.