I have one in my Baby Lock Quilter's Dream and love it. Haven't had any "problems."
I started using my Singer for piecing recently and forgot to use the genie. I noticed nests on my sewing; using the same thread as in my Baby Lock!
They must be doing something!
I have read that they last for a LONG time. I'm still using my first one. Just don't lose it when you change bobbins! They are tricky to find on the floor.