Paper is the fastest easiest manner of taking down quick notes in any situation. Then to the InBox or transcribed to Palm or Outlook.
I use my Palm mostly for reference (also as a backup for Outlook!) I will however use Palm to write in reminders and All Day Events or Appointments in the weirdest situations. Case-in-point; driving! I see billboard of an upcoming computer show with a web address - out comes Palm, open to calendar & I write in the web address as new event. I trust this and even if I make typos I fix them later.
Outlook is Hot Synced and reliable. I rarely print anything from Calendar or Tasks. I use GTD Add-In.
I would never try to push my high tech stuff to work when backs of envelopes & other pieces of paper come in handy. There is something 'cool' about emptying pockets and finding those scraps of notes taken at the end of the day. I trust this too - pockets are collection buckets and they hold info until it's time to refer to it!
I think the main underlying theme in David's stuff here it to keep dumbing down our systems until they work simply. It's like the physician's doctrine with medication - give the smallest dose that works!