I got the amp as a simple practice amp with a few features and a few Marshall tones. I also have a Marshall Origin 20 sitting next to it and a Yamaha THR10 on my desk. Comparing the three, I didn't expect the MG30 to be equally as good as the others, but I was surprised at how poorly it stacked up across the board.
Turning the amp on, it's noisy. At the same volume/gain levels the other two amps are not. The Yamaha lead channel is based on a Marshall plexi, so I turned on the MG crunch channel to find a comparable tone; one week later, I'm still looking.
Sounds: the MG sounds poor when compared to the Yamaha THR10 Marshall sim - not just a bit down, it is poor in comparison - this shocked me. The Yamaha is $300 against the $200 of the MG, but I expected the MG to at least do the Marshall tone as well as the Yamaha - it cannot even get close; extremely disappointing.
Effects: it's hard to dial in effects on the MG due to the way 5 effects use the same knob, so the actual linear adjustment space is tiny - this is a problem because finding a good sound takes a lot of tweaking. Again, the effects sound poor compared to the Yamaha THR. The reverb has two styles and is pretty light, but it's ok - it adds a bit of depth and space to the sound. I have many pedals I use with my Marshall Origin (such as a Wampler delay, TS808, Keeley reverb, etc), and I didn't expect the MG effects to be that good (and they are nowhere near), but I expected them to compare ok to the built in effects of the Yamaha THR10 - they don't.
Build quality is fine.
Late at night, I want to play the MG because it has a headphone socket and an audio in, but just turning the amp on is so noisy (a lot noisier than the 20w tube amp sitting next to it - not turned on at the same time - that I'm put off and just plug into the Yamaha instead even though it's more uncomfortable to play at my desk.
4 channels is good, but it takes a long time to find decent sounds, so the fact there are 4 memory presets is useful - you need them; once you find a sound you like on a particular channel (this may take 20+ minutes) then press save and don't change the settings of the amp again on this channel (although, if you do the tone stays at the set position when going off and back onto a channel) - this is kinda ridiculous, right, that the amp is made as an easy to use non-complex modelling amp, no PC connection required, just plug in and turn a few knobs to get a good sound, but you can't...
I had a Randall solid state practice amp, a KH edition, and it sounded a lot better than this amp.
This is quite cheap, so might be good for a first amp, but even at $200 there are better amps such as a Bugera T5 head with a HB cab - I owned that last year, and it sounded much much better in every way than this MG. I also has a Fender Mustang 20w solid state amp about 5 years ago and it did the Fender sound much better than this amp does the Marshall sound. At half the price, a VOX pathfinder is similar sound quality to this amp.
I was shocked at how poor this amp sounds and how difficult it is to find good sounds - it just reduces your playing time. I will give this away, I couldn't in good faith sell this amp on - and, I'm fond of Marshall amps; I know the MG50/100 heads sound good, I had a DSL 5w which was great once I changed the speaker. Try this amp out in person before buying to see if you like it's qualities compared to other similar amps; if you buy blind on the internet then don't throw away the box, and be sure of the returns process...