I bought the 440 soon after I started quilting, and I used the BSR for many quilts. (I now quilt on a longarm.) The sound Tartan mentions is obnoxious, but it alerts you that you are moving the fabric too fast, and the sewing machine motor can't keep up, so your stitches will be too long. It's supposed to annoy you enough so that you slow down. I thought the BSR did a great job in keeping the stitching more even than I would have managed without it. I don't think any stitch regulator is perfect - although I've been told the lightning stitch upgrade on the Innova comes very close - but I don't think most of us are looking for perfection, just for a nice even stitch.
One thing to ask the dealer is whether your BSR has the latest updates from Bernina. I wasn't aware at first that the BSR should come along with the machine for servicing so it can be updated. Have fun with your new toy.