Terry is obviously a bit biased, but the article is still spot on. You can get away with having gaps if you have the shot making skills to vary trajectories and spin, but why complicate things?
I've always carried four wedges - a pitching wedge, gap, sand, and lob. I make sure the wedge lofts fit with whatever iron set I'm gaming. Since the pitching wedge lofts have gotten so aggressive, I find myself using the gap wedge more than any other club in my bag other than my putter. So, I take great care in making sure that I'm comfortable with that club and have confidence in it. Otherwise, my game really suffers.