It's simple enough.  In fact, we've had clients complain about being confused by Link but none for VeriFyle.  In terms of functionalities though, there's much that could be improved upon as a relatively new product but I don't see those as deal breakers for a client portal.

You should try that both as an accountant and a client to simulate your day-to-day interactions to make sure it suits your needs, that you incorporate its use as part of your workflow, and that you understand it well enough to be able to answer your clients' questions about how it works.