Experience with Panasonic Dynamo hubs?
I've built quite a few of these. They work very well. They are bulkier, heavier and marginally less efficient than the SP hub but have a good reputation for reliability.
As far as servicing goes, due to the complexity of the electronics within the hub and the necessity for components to be perfectly aligned, dynamo hubs are usually considered a closed box that you send back to the manufacturer or a specialist for service. You can of course change the bearings but it's easy to end up with a hub that no longer functions as a dynamo.
Kasai have just released a field servicable dynamo hub that is, as far as I am aware, the first of its type and the only one available. However, these things are generally reliable when not abused so I'm not certain it's the big selling point it's supposed to be.