I absolutely LOVE my PDA--I have a Treo 600. I never thought I would switch from a paper journal/calendar--I had Filofax for years. But my bag was getting too heavy from carrying my stuffed calendar plus my cell phone and makeup..etc..and my shoulder and neck were killing me constantly. So I started with a Treo 270 2 years ago and upgraded to the 600 last summer.
Love love love it--I track my workouts and heart rate readings with it; track all appointments and birthdays (which I *always* forget); just loaded my entire music collection onto it this weekend via MP3s on a memory card and have been listening to music at work with it; I also get my home email on it and can IM friends on AIM, Yahoo, or MSN and also can surf the web, though on a somewhat limited basis. Plus, I track my checkbook on it--actually have replaced my checkbook with it; track my Passwords to various programs. It's all backed up nightly on my home computer, and the private stuff is all password protected. There's lots and lots of software out there for Palm OS--just things that have made my life so much easier in so many ways. I'm totally hooked.
Oh, and it's a phone, too and it has one of those silly cell phone cameras. :+
Added:
To track my workouts, I bought MySportTraining--at
http://www.mysporttraining.com/
Bought the version for a PDA only, though I may eventually also get the version for PCs. I've entered all the Cathe workouts that I do into the program, so I just have to click on them to enter them for the day. I also enter all my racewalking workouts.
There's also Diet and Exercise Assistant, but I think that's more designed for tracking your diet.
My advice is that you go to the Palm software site and see if the programs there interest you at all--most have pretty helpful reviews.
http://swc.palmone.com/us/html/
Finally, I know I sound like a raving lunatic about my PDA, and I probably am! I miss keeping a journal somewhat--love to actually write--but it has just been so much easier to actually track and see my results on the PDA that for me, at least, it has been easier to plan and improve my workout routine.
HTH!
Bunbun.