I have always used safety pins, but have begun to use spray basting for smaller quilts such as a baby quilt. I find that it is does have a monetary cost but it is effective, and I think in the end is a time saver. My only problem with spray basting was when I used the wrong kind, one designed for crafts and not quilting which gummed up my needle. That was my fault. I found spray baste on sale at JoAnn's a couple of weeks ago and got two for one. That helps lots! I can usually get one baby quilt and one or two smaller projects from a can of spray baste.
One of the gals from my quilt guild suggested light pinning on larger spray basted quilts. I have not had a larger project at hand since she gave that advise. Perhaps someone else will chime in on larger quilts. Take a chance and try a new technique. You may find that it works for you ..... or it doesn't.
I just saw a post that mentioned the fumes of spray baste. The one I use from JoAnn's does not have the heavy fumes of another that I had that was a hand-me-down. That was awful! The one I use says on the label that it is oderless and it really has almost so odor at at all.