I LOVE my iPhone for caching. It's been a godsend. I still consider myself a noob (54 caches) but I've tried caching without it and I don't know how you fine folks do it. Whenever the urge grabs me, I open the Groundspeak app, search for caches near me, and away I go.
I certainly it's nowhere near as accurate as a dedicated GPSr, but I've never had any trouble finding caches. I'm very impulsive so I can't see myself printing out or inputting by hand all the descriptions, when it was last found (in case it's been muggled), hints if i need them, etc. I love that the app finally lets you store data for offline use, as that is the one *major* drawback (MotionX helped with this but it means a lot of manual inputting). The battery life also does suck, but I just plug in to my car charger when driving between caches and that seems to work well for me.
I too was concerned about hiding caches however. I currently use MotionX for getting coords. I wait to get a good signal and take multiple readings, and my averaged coordinates look good on google maps, but aren't dead on (off by ~10 feet at times). That makes me wonder, is that just the normal accuracy for GPS, or are the google maps slightly off? Or are they dead on, and my iPhone just isn't quite as accurate as other GPSrs? I'd love some feedback on this.
Maybe the iPhone isn't perfect by itself, but I'd say paired with a good GPSr, and using offline storage, most anyone could go paperless.