Thanks! Ruby on Rails Tutorial follows the same basic philosophy as RailsSpace, including its treatment of gems. See, e.g., my comment at http://news.ycombinator.com/item?id=986514.
e.g. I fondly recall the use of the 'Haversine formula' (calc. distance on a sphere with given lat, lng) built in SQL, instead of using one of the available Geo ruby libraries/ gems (although I'm not sure, if those gems were available back in 07).
Dude, I would totally use a library today! But it was fun busting out a little spherical trigonometry for a Rails book. :-)