I love this head...my first 'real' amp and boy has it performed well. Soooo glad i chose to buy it from Ebay (new ones are around 1400 now).
Where Obtained: Ebay
2 channels...basic bass/treble/mid controls...volume and master volume controls along with focus and presence controls. It's got a gain boost on Channel 1 (the Marshall-voiced channel) and a ninja boost and mid notch control on Channel 2 (fender voiced channel). The notch control allows users with single coils to dial in a fatter tone and those with humbuckers to thin it out a bit by either pushing it or pulling it. The ninja boost adds some sensitivity to the pickups and allows you to drive Channel 2- when it's off you lose a lot of volume and get very little gain, needless to say, the Ninja boost is always turned on for me.
I use MIM Fat strat (Seymour Duncan JB in bridge and alnicoII single coil in neck with a dummy coil in the middle to cancel out some hum) and a Carvin Bolt-Kit (Currently a SD '59 in the neck and nothing in the bridge).
This thing is extremely loud for 55 watts. I play blues and classic rock...this can hit the AC/DC Angus JMP Marshall sound as well as the SRV smooth distorted sound and everything in between. It kind of souns like a JCM 800 but with more balls.
I installed an an exterior bias pot and can quickly change out tubes and bias appropriately (I've been really leaning towards the Sovtek 6L6 WXT as well as the ElectroHarmonix 6V6, both biased at about 40mA/tube).
Very straight forward/easy to dial in any tone.
Bass/Mid/Treble/Volume/Master Volume for each channel- you can't go wrong.
From what I've heard, Rivera's are built like tanks (this thing weighs a good 40 lbs). It's got nice big transformers and a well mounted PCB inside. I don't anticipate it breaking down.