I'm using Tradition. When I started purchasing my chinchillas from the larger ranchers, I kept having to switch them off the tradition onto the mazuri. I figured in the end, instead of having to switch everyone over- I might as well just switch to the feed that the people I'm buying from use. The two breeders I tend to deal with the most use the same feed as I do, so now I don't have to worry about having to switch the animals over.
I've been considering mixing a high-quality rabbit food into their mix, though. Simply because I need to get my feed twice a year- Once in ohio(8 hr drive), and once at the York Show.. and If I run out of tradition, it would be hard and expensive to get it to me.. With two different feeds going, I would have a "back up" incase I did get low on one feed.