I have some clients that tend to bring their own battings. Generally this is just fine. I've never met a batting I just couldn't quilt with, although there have been some I prefer not to use. When the quilt is finished, as long as the quilt is not lumpy or uneven in thickness, what's the harm? That is how most people see it, but don't you just want batting in your quilt?
Well, I want to show you a photo of packaged Warm & Natural 100% cotton batting. I get this batting from time to time. The batting often has little pieces of debris throughout it - little cotton plant sticks and branches. I try to pick these out, but seriously, that is just not my job, and I just hate to think that a supplier is selling this crap. The other thing I find offensive about this packaged batting is that it always has an odor - kind of like something burned in the process of making it. Maybe it disappears when the quilt is washed, but I really don't like it. The clients that use it generally say that they use it (1) because they think it is cheaper, and (2) that they purchase it at Joann's with a 40-50% off coupon. Now, the W&N that is either purchased on an entire bolt or cut from a bolt seems to be better. Before I had a business I bought their 40yd bolts, and never had problems. It is primarily the packaged battings that are inferior.
I just want to show you that it's not worth the discount people think Joann's is offering. I just did a quilt that was 77"x100" - a large twin, but too large for the 72"x90" twin or even the full-sized packaged batting. I checked Joann's site and they charge $22.40 for a queen batt - and this is on their 50% off sale. I stock a nice Hobbs 80/20 batting (shown below without any sticks & twigs, or funny smells), that would have run the client only $17.33. I do buy wholesale, so that is why I can compete with local merchants on cost.