So, when I was creating Adonomics I considered using scRUBYt for scraping Facebook. Here's why I didn't go with it:

1. It was hard to get scRUBYt to learn the "correct" rules. It tends to be over-specific or over-broad.

2. It was slow. Really slow. Using Ruby Mechanize was at least 2-3x faster, and even that was pretty slow.

3. The learner doesn't like bad HTML, but as a practical matter you have to deal with poor markup all the time. scRUBYt makes it hard to get to the guts of the system.

YMMV.