I totally agree that it is personal. I made the switch years ago to a PDA when it became clear my paper calendar was no longer working for me. Same thing with a tickler file.
Since you have a lot that comes in by email, I will suggest a great service that I use: http://www.followupthen.com/ You just forward whatever it is you want to follow up on later to them with the date you want to follow up on and they send it back to you at that date. You can even put times in.