Almost always, what is really called for are multiple interfaces:
1. a "power user" interface, stripped down, that allows for the fastest ways to do XYZ (key bindings, fast client-side validation, batch uploads, etc).
2. a "first timer" interface, with explanatory info, slower pace so people don't feel like they're getting overwhelmed or pushed in to something, etc.
I've yet to see any registrar do this. Many do offer APIs, which, for developer power users, might be sufficient. I'd suggest to this company that they perhaps keep the current version as a fallback to the existing power users that already know how to 'get things done' with it; maybe not forever, but for a while so they can learn the new interface on their own schedule at the very least.