It was a popular string many years ago. It plays pretty good, and it is super cheap. It is pretty durable. I don't know anyone that uses it anymore, but it is still available, so somebody must be using it. Not a great playing string by many of today's standards - but if it meets your needs, give it a try.
theace21, describes nylon right to the tee. Its a string all about durability. I actually know one of the teaching pros around here that uses it. It lets hard hitting players save some money, so it probably would be something you would like if you tend to break string and are not wanting to restring alot this summer.
Sometime in the last month before you return to match play, I would begin to restring with what you are used to, depending on the gauge and type of string that is. Prince Tournament Nylon is very thick, it loses tension rather fast, and the change might jolt you otherwise.