Had a play through a friend's JCM 800 2203 last night. What a great amp. A fantastic full sound, clean and overdriven. It sounded superb when boosted with an overdrive pedal too for high gain tones. This is coming from a 5150 / Mesa Rectifier player.
I'm seriously considering buying one of these soon.
The simplicity of it appeals to me. Just roll back the guitar volume for clean sounds, then just step on an O/D pedal for dirty, heavy rhythm and lead.
I was Impressed at how good it sounded at low volumes too.