Just played the amp for a couple of hours .... it's very versatile as far as the OD channel goes.
The tone is GODLY. It's not quite as high gain as the Roccaforte. It postively SMOKES the Diesel and VHT. Comparing it to the Rivera is like apples and oranges, b/c the Rivera has its own tone going on, but ... I'm gonna go on a huge limb here and say that the Splawn is better.
Pedal wise, the Splawn loves the CPR compressor pedal on the OD channel. Unless I'm going to be doing very specific tone-shaping, it doesn't even need the Big D overdrive pedal! The reason I love using an OD in front of the amp is because of the 3-dimensional sound you get. The Splawn has that right out of the gate. I'm going to continue experimenting with that combination, though. I haven't used my boost pedal with it yet.
I haven't put in enough time yet to make any definitive conclusions, but I can already tell it's a godly amp.