Sorry but the advice to "don't use an IDE because Rails doesn't need
one" is as dated as this book.
I try an IDE for Rails about once a year -- precisely so I don't get
stuck on dated advice. Inevitably, I go back to KomodoEdit.
I use NetBeans for JRuby/Monkeybars development. I love it for that,
but it is completely inappropriate for Rails work.
Today's IDEs give you significant advantages over a text editor, to
name but a few:
Doesn't seem to work in NetBeans.
No Rails configuration required, already understands the Rails
structure for easy navigation.
That's one of the few things I miss about Aptana, but it's not a big
enough advantage to put up with the rest.
Integration with Rspec et al; run tests with a click, visual debug
I run tests with *no* clicks (with autospec in the shell). I don't need
an IDE for that.
Integration with Git; browse your changes, 1-click to diff, etc.
NetBeans' Git plugin is great (except for some annoying bugs), but
except for the cute mouseover diffs, Komodo + GitX is at least as good a
Netbeans is good I agree (plus has an awesome flawless Vim plugin),
but I now use RubyMine which is better (although the Vim plugin
blows), but it's not free though.
I won't pay for a text editor or an IDE. There are so many good free
tools that it seems silly.