It's so simple it's silly.
PDAs are clunky, expensive, and can't import from the apps you want.
Notebooks are bulky and, if you're a jeans type of guy, are difficult to carry. (Men with jackets, women with purses, or anyone with briefcases, you can stop reading.)
Notepads get dog-eared and tattered.
Go change the paper in your printer.
Start using 24-pound paper. It's nicer, anyway. I prefer the HP LaserJet paper, 24lb, 96 brightness.
Now, when you have somewhere to go, print out the notes, actions, etc. you'll need. Fold it in quarters, and stick it in your pocket.
You now have a notepad. It's stiff enough that it doesn't need backing cardboard. It's flexible enough that you can slide it into a jeans pocket, or even sit on it without hurting your back. Any program can export to it. You can capture other things on it. At the end of the day, when you empty your pockets, stick it in your inbox - or, better, retype your notes and put them into the inbox. Cost: a few cents.
Done and done.