I've used one for about 15 years. They are fine up to a point. Large holsters such as my full flap ROA holsters must be folded to pass through the throat of the machine (a real PITA) they are not very good for long runs such as in large belts. With practice you can get very good results, however there a lot of these machines that just sit because the owners got frustrated and gave up. Tuning a Boss and keeping it in tune can be very frustrating until you thoroughly know the machine.
My personal opinion, I would not get another one. I don't know what I would get, but it would not likely be another Boss.