Definitely a beast. A picky one, though. You'll find a sweet spot on each channel and probably never leave it without the introduction of certain pedals, as it's just not an amp that consistently kills while sweeping through EQ settings. It's true that the loop is a bummer. As you sweep through the range of the loop pot, there's a considerable volume swell at 12:00, with 0% and 100% wetness being the lowest points, volume wise. Some people have the loop modded to run 100% wet all the time and leave the setting stationary at noon for volume.
There's a common complaint of a 'fuzzy' characteristic around the notes on channels 2 and 3 that is more or less noticeable when swapping various pre's, but is always present. I came across a tip around here a few years back that if you run the channel volume full tilt and adjust the master to taste, the fuzz is noticeably mitigated. People thought that sounded ludicrous, but I have noticed the difference and run it that way, myself.
I always preferred greenies with the cobra. Absolutely kills in an Überkab. They're not joking about the low end. The bass and Deep in the power section will rattle the teeth out of your head. But I know that Adam D ran it with V30's in a Mesa cab for his lead tones on the Times of Grace project and I thought it sounded incredible.
And yes... Surprise, surprise, it sounds best when cranked. If you have any use for a clean channel, it's absolutely pristine and can be driven into gnarly breakup. Unfortunately, if you don't have the time or patience to sit down with the amp and take note of the intricacies - or tediousness that is the cobra, it'll be hard to appreciate it. But if you give it some time and experimentation, it'll slay. Guaranteed.