When not used against front-line tanks the T-55 is probably the best general purpose tank in the world. It is to tanks what the AK-47 is to rifles: cheap, easy to maintain, durable, reliable and deadly.
Although any tank is dangerous, this is not a good tank by any stretch of the imagination. I have been in a T-55. A piece of junk, especially if it has not been well maintained over the past 12 (40?) years.