I've heard nothing but good things about them. I plan on getting one because I'll be shooting the Nitro ammo this year and that tube is what they test paterned from.
My dad used Rhino Choke and Nitro Hevi 4x5x7 last season, and I used Nitro Hevi 4x5x7 out of a MAD SuperMax choke. My dad killed 2 in 2 shots and I killed 8 in 9 shots. The one I had to shoot twice was running on the first shot. We shot a couple of birds at 40+ yards and just dusted them. The patterns in both chokes are very good. If you have a good aftermarket choke, it will most likely perform well with the Nitro Ammo. Can't say enough about Nitro Ammo, I won't ever shoot factory loads again! Just got a Browning Gold 10ga and will buy Rhino/Nitro for it.
WM