I have one also and it is nice, but you really don't need it. There are lots of lessons out there that will teach you to do the corners without having to buy a tool. I think that sometimes we buy these little tools or aids because we can do it the "old" way, just to see if it is easier. Sometimes yes and sometimes no, but I do it anyway.
If you have only been quilting a short time, get the basic things, a couple different sized rulers, a good cutter and mat and spend the extra on the best fabric you can afford. After awhile, you will know if you need any additional tools.
Pam