In a workshop someone asked Daryl about the pass. His answer was interesting and relevant. He said (I'm paraphrasing): even when the best technicians do the pass you can almost always tell that something has happened.
I personally agree. I've seen many great magicians do a pass, and I've only ever seen one that was completely invisible (Eric Anderson's waterfall pass -- incredible).
So my personal opinion is that learning the pass is not an effective way to spend your time if all you need is a control. There are many completely invisible ways to control a card which take many hundreds of hours less to master -- hours which you can spend on things that are much more important than controlling a card.
However, there are many uses of the pass where it is not, strictly speaking, necessary that it be completely invisible. Jamy Ian Swiss did a wonderful routine in the Castle Close Up room recently, in which he does a dozen or more passes more or less in a row, producing color changes, transpositions, etc.
To most of the audience Jamy's passes were invisible, but even if you were sitting at an angle where you could see a flash of movement to the deck, this did not diminish the effect. The card is changing -- there's supposed to be a visual change to the deck.
I do not know of any way to recreate Jamy's wonderful routine without putting in the time to learn the pass. This, I would say, is the ultimate benefit of learning the pass. Whether that benefit is worth the time it takes (Jamy spend an hour a day every day for 18 months learning his pass, and I'm sure he still spends many hours a week keeping it as good as it is) is up to you to decide.
Personally, the only pass I use is the midnight shift, for a visible rise in my ambitious card routine.
I hope this provides a perspective that is maybe a little different from the usual stuff you read on this interesting subject, which I believe is what Robert was looking for.