I used Cachemate on my Treo for a year or so, and then when my work required me to use a Blackberry I was worried about paperless caching... so I started using Cacheberry a few months ago. All in all, I am very pleased with the app. I still download to my Nuvi to get me to the cache area, but switch to my 60CSX and Cacheberry once on the trail.
Pros:
User interface and navigation
Search features and filter on searches
Email yourself all your notes from each cache with links to take you to GC.com
Swap to GC.com from Cacheberry for last minute log info
Sort features (especially sort by GPS coords so all near caches are sorted together
Support by the developer. He continually makes upgrades based on user feedback and is very responsive on his forums.
Easy updating of new versions
Multiple database support
Cons:
Large database support. I like to load 2500+ caches into a single database. Not practical with Cacheberry. I have to break it into smaller databases for performance and load time efficiency. Still works, but an inconvenience.
I really like the application and give a 2 thumbs up!