depends on what you mean by good?
Do the get the job done? yes they funnl exhaust gas out of your engine nicely. Are there better pipes on the market? absolutley.
My expirence with MAC has been hit or miss. They are cheap pipes and it shows in the cheap metal they use. Thin walls and prone to rust out. Usually with my macs I try to paint inside so slow the rust out but it wll happen over time. For some models there are fitment problems. I have had plenty of success mounting mac pipes to cb750s and a 550, but there was one that was a major pain in the arse to fit and required some grinding and some welding.
I'd say with mac you get what you pay for.