I have had a Z22 for almost a year now. I like it alot. Better than carrying around a binder full of paper. Everyone is right about the "direct sunlight" problem. Just gotta make your body into a shade, and even then that doesnt help. I usually wait till I get back to the car.
I usually number the cache, as I find it, in the PDA. Butif you really feel like it, just go back through the list and check your times (if you mark it).
Cachemate is a nice little program. Works good for me. GSAK and it get along. Took me some time to learn both, but I got them figured out.
I too had thought about the "getting ruined" factor. Only have dropped the PDA once in the snow, it was ok. Now I make sure it goes back into my pocket, cache bag, or cradle as soon as I am done.
battery life is pretty good. When it is cold, it dont last as long, but what batteries do? Might look into the car charger for it, just in case. I know I can get a whole day or 2 out of it on a full battery. Only turn it on when it is needed and then right back off. I did get an aluminum case for it with belt clip. Works out nice.
Right now I am tryin to find a map program for it, so I dont have to print out maps all the time.