While I don't completely disagree with Ian, I do on one point. They are not the worst invention as they are KILLER bobber lines. He's right, they don't cast overhead, they don't single hand, and I wouldn't ever swing a fly with one, but if you're throwing a bobber and junk, they are the cat's meow. I will also say from personal experience, the Rio switch line is by far the best that's been put out there so far. I don't like the speydicator because it's overlined too much and the switch chucker....well....sucks. The switch line has a longer and head and can be mended from greater distances than the chucker.
I guess I skipped the whole nymphing thing because when I'm fishing bobber water I just run my pin due to its overwhelming superiority in all things suspended. I must quantify that I do actually own a Rio Switch line and I pretty well hated it from the get go and if anyone wants it I would give it to them because I would feel guilty selling it.
I was wondering about this too but the conclusion I have come to is that if you are goning to bobber fish it is best to get a setup designed for it. I was jelous of your 10 ft single hander for nymphing. I think I want to look for something like that now.