OK, just got done playing for around thirty minutes or so.
Experimented on both the clean channel playing clean, then moved it up to the crunch mode on the clean channel with the mid boost activated.
Also played all three switch positions on the higher gain channel.
It sounds darn good with the headphones only with the speaker switch turned off, and set to either closed back or open back.
I am using Sony MDR 7506 Studio Professional headphones.
http://www.amazon.com/Sony-MDR7506-Professional-Diaphragm-Headphone/dp/B000AJIF4E
You do have to turn the volume knob up higher than you would if you were using just the speakers.
I can turn the volume down on the amp and the cans sound good, or turn it up even higher for more "feel" when wearing them and it sounds great.
Perfect for jamming if you do not want to disturb anyone around you.,
I have zero experience with the Mesa standalone product called the Cab Clone, but the one built into the amp sounds great.
Have not tried the DI out using a cable to my Zoom R24 recorder, but someday will experiment with it.