I got a Bernina 820 with the BSR in July. LOVE, LOVE, LOVE the BSR!. My free motion is really improving. I consider it worth it.
Actually the Bernina 820 was the pnly machine I really considered because it had the only 2 things my other 2 older machines did not have- the BSR and a 12" throat.
My advice would be to take a FMQ, get a couple of books on FMQ and practice a few times a week. If you don't feel that your FMQ isn't improving, then the BSR may be your answer. There are lots of talented quilters who do great stuff without the BSR, but I'm not one of them. I need all the help I can get. Good luck