Lately, I have neglected the R2 channel on my III. But when I first got it, I was instantly in love. It really blends nicely volume-wise with the other channels, despite the lack of R2 Vol mod on my amp, and it's by far the most versatile of the three channels. Using the neck pickup of my Les Paul, and the Volume 1 set around 6.5, and the guitar volume rolled back, I can go anywhere from an alternate clean tone, to a Vox-ish crunch. On the bridge pickup with the same amp settings, and dimed guitar volume, it sounds like a good old Tube Screamer pedal. And with brighter settings and same guitar settings, I can get a very nice Marshall tone out of it. Crank the Volume 1 to about 8, and you get a high gain tone similar to that of the lead channel, but a little darker.
But lately, I've been tweaking in the Lead channel only, contemplating the C30 mod, to get more of a IIC+ tone.