I did a kit-up for my sister's DWR, minus backing and batting and I really liked it a lot. It was nice to have everything together so when I started on it, I had everything I need. I used to just get enough fabric to get a quilt started, then buy more later but I found that my UFOs were getting out of hand because over half of them always had the note 'don't have enough fabric to finish' in them.
The other issue I got rid of was not cutting all my pieces at once. I wasn't strong enough yet in my rotary skills that I felt I was losing accuracy by cutting everything all at once, plus I was excited to get the quilt going. Now when I make a kit, I get everything together I need, I do all the cutting I need to do, then re-kit accordingly. It's double the work, but at least I know I have everything together, in order, ready to go so when the big day of starting it arrives, I can just sit down and sew.
I'm hoping to change things this year by adding the backing and the batting to the kit, but it's just going to have to be a wait and see type situation. I've finally built up enough background fabric with my Muslin, black and white fabric bundles that I think I can swing the backing and batting, but until that day comes, I'm going to continue just working on the quilt top fabric, thread, quilting stencils, etc.