Great for fun, but don't overdo it. Blitz is recommended to test out variations, relax, take a break from real chess or simply have fun, but if you intend to improve in chess, don't make a habit out of it. Don't be one of those guys who trolls the chess forums playing 10,000 Blitz game a day.

Is it good to play blitz chess?

Playing blitz chess gives you a lopsided set of skills. It does improve your ability to think quickly, and to find a "good enough" move for most situations. In this regard, it is good training for the times (in tournaments), when you get into time trouble.

Is blitz bad for your chess?

For many of the same reasons that blitz is so fun – playing out many games in a short period, quick positional and tactical assessments, and unsound sacrificial attacks – blitz can be very harmful to your serious, slow chess game.