This article is a wonderful demonstration why simple methods piped together is better and easier to use than a giant monolithic application like awk.
Now, there's stuff that never sticks in my brain (tests in shell, sigh). But generally there's less syntax and therefore less to remember in a chain of greps. Composition of simple piece is easier to understand than one equivalent and therefore more complex piece. Heck, the power of the shell is predicated on this idea.
Perhaps the best part about ack is that it's simple to restrict your search of files to a given pattern with a command line flag rather than using shell globbing. You could wrap invocations of grep with a shell function or another script, but that's still not great.
But that too seems like a demonstration of something. The more "simple" methods with obscure names that populate the Unix toolbox, the more confusing it gets. I've gone from find to locate recently, for example, but their functionalities kind of overlap and so when I do find, I'm rusty with it.