They aren't all that great. They basically just do one thing... overedge a seam. If you aren't planning to make garments, I don't see any reason to get a serger. Some people use them in quilting, but I don't see why, for two reasons. 1) The serged seam is a weaker seam if not accompanied by a regular line of stitching, and 2) there is no reason to finish the edges of quilt pieces, as they will be totally encased and then quilted over.
I have had a serger for about 30 years because I used to sew all my children's clothes when they were small. I mostly just quilt now, and only use the serger when I am making dresses or blouses for my grandkids or for charity.