I haven't played one in ages, but I heard a guy messing around in one at whisper-quiet volumes in my local guitar store the other day...
It's not bad for what it is. Unlike the VS and AVT series, it makes no pretense of being a "hybrid" amp, so there's no marketing push about "tube-like distortion" or anything (which is, IMO, BS, since so much of what makes a tube amp so magical is the power amp, and with just a single preamp tube, it's impossible to do a high gain, multi channel amp with cascading gain stages, so most of the OD is still transistor in origin). That said, it wasn't a half-bad sounding amp- Very "edgy" and agressive without sounding overly buzzy. The guy was playing with a medium-ish gain level that handled EVH material quite well, although with a bit more snarl in the high end. And while it's tough to speak for the dynamic response when you'r not plugged into the thing yourself, the sounds coming out of the speaker were certianly good enough. It's more of a modern distortion voice, although you can probably approximate something a little smoother and more vintage with the right EQ settings, but once again, that's all in the power-amp distoriton which you're just not going to get here, so don't expect it to be hitting that "woman tone." However, for modern marshall crunch, this thing can definately hold its own. I was definately pleasantly suprised.
As for the clean channel, i didn't get to hear it, but my experience with marshalls is that their solid-state clean channels are generally pretty lifeless. Flat, thin, and uninspiring with none of that warmth or breathy shimmer you get from a good tube amp. Then again, most people don't buy marshalls looking for their clean tone, now do they? (That said, the cleams on my TSL are actually quite lush, especially with singlecoils, and the old JTM-30 combo i used to own WAY back in the day had a quite cool clean channel- bright and VERY focused with little bass response, but great for bluesy leads- think maybe Buddy Guy).
Only real qualm here? If you go for the MG, make sure it's one of the ones with a 12" speaker, or at the VERY least a 10. An 8" just won't give you proper bass response.
If you want to go slightly more upscale, pass on the VS's and AVT's and go straight for a DSL-401. (or the 201 if you can still find it). If you're goint to pay any kind of an upcharge for tubes from marshall, it's pointless to only go halfway, and the DSL series are GREAT sounding amps (a friend's 401 into my recto 2x12 sounded nearly as good as my TSL).
Oh, and DON'T scoop out all the mids.