I'm an emacs user and have a Model M keyboard at home (bit too noisy to use in an open plan office) and while it was incredibly expensive to ship it from Kentucky to London it was the single best investment I've made in my computer ergonomics and prevention of repetitive strain injuries.
I'm a vim user, though I'm sure this setup would still be a lot better for emacs users too from an RSI perspective (esp. compared to cheap rubber dome or laptop "chiclet" keyboards).
Haven't used one but they seem like a good choice. I would focus on the key mechanism (apparently the Das Keyboards are the same as the Model M) in this respect and the size. Larger, more spacious keyboards are a lot better.
