If you need read performance or abstraction from a datastore look no further.

Really good .NET client that is very easy to use. The management studio is excellent and puts anything that Microsoft or Oracle have to shame. Very quick to develop with once the complexity hurdle has been overcome. Initially using it can be a bit painful until you fully grasp the event sourced nature of the indexing.

Oren will usually answer any question you post about his product. There are not many founders and designers of systems that make the same effort that he does in supporting both his product and the community in general. The documentation can be a bit overwhelming due to the complex nature of the product but everything is there if you need it.

[RavenDB can handle] anything abstract. Being able to select an interface or base class from an Index brings a whole new world of flexibility to my designs. Having a spit of CRUD documents and Data Transfer Objects through indexing also makes it very easy to build with, once you get the hang of it. The biggest challenge is getting other developers to understand how it works. It is more complicated than your average SQL solution and does require a smarter developer to use it.