A C++ Repl while really interesting and nice and all that--- does not an AWK make. Given the examples shown, you can do some AWKish things, but so can Perl or Lua or whatever... Tis cool though, gotta give it that!
Well, it also probably compiles a full C++ program before running it. So performance would be terrible. I think this was made as tongue-in-cheek with all of the ruby awk stuff we've seen lately.
What I take out of this is "the unix command line tools are there, learn them and use them."
Interactive performance? SCC compilation is about 1 sec on my old laptop with warm cache. Good enough for command line tool. Or do you mean run time performance? Run time probably faster than anything else.
For interactive use - yes, it's good enough. For use in scripts - it's probably too slow. But you can use compiled binary. It is saved under /tmp/<user-name>-scc