I have a Bernina 430 and the BSR. I love the BSR but still need a lot of practice on making my FMQ designs look the way I want them to! I do think the BSR is a valuable learning tool and a "security blanket" so you don't have to worry about stitch length, but I don't know whether I would buy a new machine just to get a stitch regulator. On the other hand....Berninas are fantastic machines and you won't regret buying one.
Anita