I like that you can send in pedigree information, which makes it easy to get started with your new zoos animals or even just help out an established zoo! It's free but there are some limitations (eg not many different types of livestock).
The user interface needs work - especially when searching through records by date range would be helpful. We have been able to use this software as we've gotten more involved at our non-profit and now also provide technical support to others who want this kind of service.