I must admit I was eager to have the series done with. Four games can strain one's walet so I waited for the price do drop down.
.hack hasn't changed a bit since the first game, for the good and bad. It still has the same anoying dungon design that repeats it's self over and over again. But this time the story heats up kinda like .hack//Mutation (Part 2) did. It's a slight change in pace over .hack//Outbreak (part 3) and that kept me intrested enough to beat the game and unlock most all of the secrets.
I wouldn't recommend buying .hack//Quarantine unless you have played Part 1-3 first or you'll be quite confused with the story. But all in all I think it was a good game and I recommend it to other RPG lovers.