I generally do not buy kits as I have a ton of fabric and a good part of the fun for me is playing with the colors. I also prefer scrappy quilts, so a quilt with a limited number of fabrics doesn't usually appeal to me.
However, I am seriously considering giving up attending my yearly quilt retreat so I will have the $$ to buy a kit for a beautiful queen-size bargello from Keepsake Quilting. I do love the colors and since it is all in solids, and I don't have many, I would have to buy almost all new fabric to make it instead of being able to pull from my stash as I normally do.
I agree with the previous poster about the cost of BOM's. When I realize I'm making a committment to spend $400 or $500 for the fabric alone, and then add the cost of having it quilted on top of that, it makes me think twice ...