Very curious to see how well this works in practice.

An excellent example of a usable predictive interface is DataWrangler from the Stanford Vis group - http://vis.stanford.edu/wrangler/app/. Bit of a learning curve, but well worth it if you're working with semi-structured text data.

The paper describing their philosophy and the predictive interface is here: http://vis.stanford.edu/files/2011-Wrangler-CHI.pdf