I've got the Fire and I wouldn't write it off as useful for geocaching. For several years, I've used an iPod touch with geocaching software that lets me download the webpages, hints, etc. and carry them with me. (That way I didn't have to preplan my trips...I always had the info available -- until it got too old and out of date.) Anyway, I'd use that and one of my many, many handheld GPSrs to go caching. I didn't need anything but WiFi before I left the house (and I downloaded one of the sets of caches I generated with my Premium membership here). I'd like to do that with the larger Fire, but you can't download the software. Amazon allows (and secretly endorses) sideloading of the geocaching applications, but that requires the ability to find (and buy where applicable), the APK executable. I'm too paranoid to download an APK from anywhere but the developer's site. Unfortunately, none of the geocaching software vendors have been willing to sell the android software through anything but the Appstore. (BTW, several have been sideloaded on the Fire and they work great for reviewing the webpage for a cache while in the field with NO CONNECTIVITY required -- just no GPS, so it's info only and paperless logging that gets uploaded when you get home.)
Developers -- make the APK available for the Kindle Fire!