I'm having some stability issues with my Treo 755 at the moment, so I haven't tried it yet, but it looks like an interesting product: http://www.activecaptain.com/index.php

i would be concerned about exposing my pda to water (and salt, in my case). also not sure how readable it would be with a small screen at speed and in direct sunlight.

Screen size would be an issue, although I'm not sure it is any worse than using a portable. The resolution on modern Palm OS phones is 320 x 320, which I believe is higher than many portables. I wouldn't want it as my primary source of charting info, but thought it would be fun to have a chartbook in your pocket any time you wanted to look at it and have as a backup source of information.

For sure not useable as a primary unit. I agree that having it as a chart you can check out, plan upcoming trips with would be nice.

I use a chart program on my pc, not on the boat, but at my desk as a way to be on the water (in my mind) during the weekdays.

I gave the program a try. It actually works pretty well - more screen area would be nice, but it zooms in and out quickly so you can find an area of interest, then zoom in to see detail. It is quite usable. I'm not going to spend the $49.95 to buy it (you can use it 20 times for free before it shuts down) since I already have a portable GPS and a couple of chart programs on my laptop, but it is a nice application.

Another Palm OS program I use on my phone is Tide Tool. It is a shareware program that allows you to get tide/current data for all of North America. Very nice application.