I've had my JTM-60 combo since new, about 10 years now. I really like it. Channel switching (2 chan), 4 ECC83s and 2 EL34s.
Mine is the 2-12 combo (JTM622), I just found a matching 2-12 bottom cab for it.
My JCM800 (4010) combo stays home, I gig with the JTM-60. No it doesn't sound quite as good as the 4010, but close enough and the channel switching is something I need. If you're looking for 'Fender' clean, I don't think you'll find it here. If you're looking for decent Marshall crunch, you will.
The JTM60 became the JTM600 became the JCM600. Other than the exterior changes, I believe they are the same amps.
From Dr Tube: "The JCM600 amps were introduced in 1997, superceding the JTM60's, and discontinued in 2000. Circuit wise the JCM600 amps were identical to the JTM600 amps. The styling was changed to more modern standards though."
I have read many complaints about overheating problems, guys installing louvers and fans etc. I've never had a single problem with mine. These amps do seem to want proper warm up - switch on power, wait a couple mins before turning on standby.
Try it out, crank it up. I think they can be a really good buy. Ripper, if you have a 4-12 cab on hand, try it. My head really loves the 4-12s now.
Channel switching, master volume, tube Marshall. One hell of a lot better than most in the price range.
---
I just looked at that one on Ebay. If I didn't already have too many amps, I'd be chasing it.