I decided to pre-wash everything when my stash was very, very small. I washed everything I had and since then have washed everything as soon as I buy it, so the entire stash has been pre-washed (except for fabrics that I buy specificlly for OBW's). If I don't want the crinkled look then I also wash my batting, but usually I use W&N and don't wash it and so I do get the crinkled look. I try to buy quality fabrics (at a good price) and I find that the feel of the fabric is every bit as good after it is washed, sometimes nicer because excess sizing is removed.
You will find that there's always a big debate about washing vs. not washing, so you can do either. As far as I can tell, though, the main reasons people do not wash are that they like the crinkled look and like the feel of new fabric. Since I believe you can get both of these after the fabric is washed, I think the real reason most people don't pre-wash is that they don't want to spend the time it takes to wash and press, especially if they already have a large stash that has not been washed. To me, the advantages of washing (eliminating the problem of bleeding fabrics, getting rid of any toxic chemicals on the fabric, removing excess sizing that might disguise the fabric's quality) are overwhelming, so I pre-wash.