Hacker Evolution is, ahem, an evolution of Exosyphen's previous hacking games, of which they've developed several over the years. This is a good thing, as the current game is intelligently thought through and polished, and the puzzles cleverly designed (if at times frustratingly hard). That is, of course, a big advantage of reworking the same theme: you improve each time.
Many will compare Hacker Evolution to Introversion's Uplink, also an excellent game in this--well, there aren't enough hacker games to call it a genre, but "of this type" will do. Hacker Evolution =feels= more like you're actually hacking because of a design decision that in almost any other type of game would be obviously incorrect: The game is largely played on the command line.