Wow, impressive homepage from a marketing angle. You hackerheads would do well to print out this website and hang it on your wall.
Note the use of: quick, clear description; testimonials; subscribe box so you can keep in touch with the project; a top-ten list; and no-frills detailed information.
It seems like it is only faster because it applies a bunch of heuristics to avoid searching certain files and directories altogether. I use "ack" myself and it's quite nice, but the heuristics aren't perfect: ack won't search for strings inside yacc grammars (".y" files) by default, for example.
Then end result is that, on the same search, ack is approximately 5 times faster than grep. I ran a few test cases myself and got similar results.
But the real reason I like it is the perl compatible regexes. The differences between perl regexes and gnu regexes are just big enough to be an annoyance.
In that particular case, ack's performance advantage seems to arise mostly because of a bug that causes GNU grep to be terribly slow in multibyte locales:
Note the use of: quick, clear description; testimonials; subscribe box so you can keep in touch with the project; a top-ten list; and no-frills detailed information.