I only did the online version of the "book", so I don't know if we're talking about the same thing. I wasn't aware of there being videos, so no, I haven't seen those, but I have viewed numerous Railscasts since completing Hartl's initial introduction and those are invaluable too.
During the tutorial, I faithfully followed almost everything presented, including the extra work (e.g. using Postgres instead of MySQL so that the dev environment matches production more closely). This included TDD and Git. Git has been fairly painless because I have used Mercurial before and they are quite similar.
With my side project, that I started right after completing the tutorial, I initially used TDD extensively, for the basics of the model, but once the foundation was laid, I can't say that I have kept my test coverage up. I assume my story is not uncommon in that respect.
