Would a hard to learn UI be acceptable?

Most often I see software aiming for easy to use. This usually does not mean easy to use, but easy to learn.

For example, vim is really easy to use, but extremely hard to learn. Most webpages are easy to learn but hard to use (delay in response time, multiple mouse clicks, etc.).

Many programs (like MS Word) tries to be easy to use with and easy to learn UI that they combine with shortcuts. This works rather well, but it's still aimed towards easy to learn as a primary objective.

For professional users that works heavily with a program I would think that easy to use should be more important than easy to learn. However I sense that it's not always the case.

So my question is, is it okay to produce easy to use UI rather than easy to learn UI for a professional audience?