First of all, I'd like to talk about the thing that will influence you the most. We're making every effort to make the use of NServiceBus (particularly it's auxiliary processes like the Timeout Manager, Distributor, and Gateway) much, much easier. What this means is removing much of complexity of using these capabilities by hosting them within the same host as your own process, but don't worry, we'll make it easy for you to turn them on and off using profiles. This will enable us to configure all the routing to these processes for you, but if you want, you can always go back to the manual approach in version 2.x. This is where I'll be investing most of my time.
Fourth is RavenDB integration. I'm happy to say that a licensing agreement has been reached that will allow users of NServiceBus Standard Edition to use RavenDB for things like Subscription Storage and Saga Persistence at no additional cost. This will save you from having to haggle with your DBAs anytime you want production-ready storage for NServiceBus - it'll give you a much more cohesive deployment without worrying about overloading your existing relational databases. I'm happy to welcome one of our newest committers, Jonathan Matheus (http://www.linkedin.com/in/jonathanmatheus), who is making this happen.
We're also looking at stronger Visual Studio integration, possibly to the level of providing model-driven code/config generation. We'll see if it's feasible to get that done within the 3.0 timeframe, or whether that will be delivered as a separate download afterwards.