I couldn't agree more. GTD lends itsself to a variety of planning tools including very simple, basic ones and the 3-ring binder is efficient and powerful. It also benefits from being dirt cheap and having almost no learning curve.
The way I make the calendar section work is to set up my recurring events in the Google calendar online application, then print out the monthly pages (and/or weekly and daily as desired) and punch them for the binder. This eliminates a lot of re-writing of recurring events and provides free refills on demand. For appointment reminders, I set my cell phone alarm. Or Gcal can send me an SMS message if desired.
My contacts are just a typed list, printed out, punched, and inserted into the binder. Updated when necessary and reprinted. I keep the document on Google documents.
If I ever lost the planner, I could at least regenerate most of the calendar data and the contacts list pretty quickly and easily from any computer.
Definitely bulkier than a PDA, but well worth it for me.