I have been using the Geocache Navigator by Trimble for awhile and I love it. It has everything you could want when searching for a cache. Radar (when zeroing in on gz), compass (when moving faster), map (ariel, street and topo) and details about the cache. You can also get the hint, and logs.
Then to make it even better, you can mark it has "Found" or "Did not find" and it adds it to your Field Notes on your Profile page on Geocaching.com. When you log on, you can log your find and done.
I think it's a great product and well worth the $19.99.