If anything the icons would make it more suitable for "heavy use" because once you get used to them they are an improvement to the old text, defeating the point of this superficial article even more.
Forcing a user to stop and think about "what does this icon do" -- and yes, even your "heavy" users are going to run into this -- just to make something look pretty is basically always a bad idea.
No, this is incorrect. I'm a heavy user of Gmail, and I still can't find the damn new refresh button. How many weeks should it take for me to get used to this so-called "improvement". I preferred it when it was text. I just don't see the new spiral icon thingie as "refresh".
Another way to look at it is if you make an improvement to something I don't care about, it's not an improvement. Especially, if it makes my job harder.
You need to actually measure what users do, not generalize from unsupported assertions.