I have a tuba in its 3rd year, some euphs in their 2nd. The horns seem a little easy to dent in comparison to Yamaha euphs. Valves so have have been good. Cases are not great, straps are starting to come off. For the price, they're pretty awesome.
Several companies sell essentially the same horn from the Jinbao factory. Wessex, Tuba exchange, Mack Brass, they're all the same thing (more or less). Mack is the lowest price I've found.
Customer service has been great. I needed some replacement screws, they shipped those out to me free of charge.
Overall, if you can't afford to buy a "name brand," Mack is a solid choice.
I need to get some new brass. Mainly trumpets, trombones, and tubas. We are good on euphoniums and are alright on horns (though we could stand to replace some). I'm looking at Mack Brass, but I would like to hear from those who have had them for a while. They are inexpensive, but I'd like to know if they are "cheap" or if they have held up.