I was first in line at Carvin to get one. Still have it.
I love it, the tone is great because it's pretty much "my" sound. I occasionally toss an MXR Wylde OD in front of it for freaky gain and a slight change of flavor to my gain shape, but the amp doesn't need that. I tend to use a Wampler compressor in front as well, but that's my own crutch and no comment on the amp.
Anyway, I love it, it's versatile and it can bring the hi-gain. Maybe it's not a Fortin NATAS or whatever but I don't need that much gain, I'm good with the nearly-absurd gain I have now.
If you have specific Q's about it, I'll see if I can help.
The original V3 is a great amp. It has its own sound. Just a couple points I think that you need to realize are that the amp is not idiot proof. Many people dial the V3 in based on their pre conceived ideas of how the controls should look when dialing in an amp rather than their ears. This can lead to shit breath tone and thoughts that the amp fails. Many people claim the amp sounds fizzy and I swear that 90% of these claims are from people who have not learned the amp properly. The V3 has not only a treble and presence knob but also the global bright control as well as the expanded eq switch. That is a shit load of high end frequency control. And sometimes people go a little crazy with those things not having previous experience and dial in a crap tone then blame the amp. So if you get one just be fair to it and use your ears, not your eyes.
The only negative to the amp for me is that global control panel. Its a great sound shaping tool but at the same time I hated it. The reason being you couldnt turn it off or assign it to the channels you wanted to use it on. So if you dial in the tone you want on the clean channel its quite possible you wont like those global control settings on the dirty channels. Ive heard people say that that is why you have the presence and treble knobs to fine tune but then that just makes the global controls pointless to begin with. And still thats not true as the controls affect different frequencies. The V3 sounds fantastic, you just need to be patient with it.
as for the V3M, I cant recommend them. Honestly aside from the name and the similar look the amps sound nothing alike. I wanted to love the V3M as it didnt have those pesky globals but the amp has very poor sound. Some amps you struggle to find a bad tone, the V3M is the opposite. I struggled to find a good one. And if your into metal you can forget about it. For a lack of better description the V3M sounds like a fart through a tubescreamer, I shit you not. A good example of the poor tone is Carvins very own demo video with kevin michael from sledd. The ONLY thing that gets that amp to have any definition and clarity is a TS type boost pedal. Without it I would have to rate it in the top 5 worst tube amps for rock and metal in recent years.
To me, the V3 is "Poor Man's JSX". It's a fine amp, but it is what it is, and what it is may not be right for you.
I had no problem getting nice tones out of all 3 channels, but that was me plugging into it dry at a local GC as well as a local Carvin equipped rehearsal studio. I never configured my PXTL as an effects processor, channel switcher using the 4 cable method + the midi cable, so I can't speak for how it does or does not work with effects setups.
Mine sounds alright with effects, but it's not doing anything over-the-top like 4-cable method or anything along those lines.
I have a Wampler Compressor and a Wylde OD on the front end, and in the loop I have Rocktron delay, Rocktron Reverb, and Wylde Chorus. It works well enough, but I'm not that into effects so your mileage may vary.
I can't comment on the Micro, but otherwise I think I'm in agreement with PurpleDC. It's one of those amps like a Mark V where you need to know what you're doing or you can quickly make it sound rather undesirable. And yes, you have to mind the treble and bright controls, or you can get into the world of fizzy high-end. The Vintage 30s in my Mesa Recto cabs aren't especially shrill on the treble end, but some speakers might not deal well if you crank up the bright side on the V3. So I guess the solution is this: don't.
Great amp, but yeah, maybe not for everyone.