I have a Bernina 770 and I bought the ruler foot for it. I've used different rulers: Westalee, Angela Walters, and one from Bluprint. It's really fun. I'm better at that than any other machine quilting but trying to get better at FMQ.
Anything with the Bernina name is pricey but once you have it you have a nice product. My 150 is 18 years old and has never had a problem. I'm hoping the same for my 770.