I use this amp as my home studio amp, practice and noodle amp. It does all 3 jobs well, with the distinctive Marshall sound we know ( and most of us love).
So, the pro's:
Typcially Marshall. If you have owned a Marshall, the controls will feel natural.
Built like a house. Mind you, this is not a top-of-the-line Marshall, but it still comes in at 20 kilo's. DSL may be the "affordable" range, but the first impressions do not align with this truth. It feels solid, and like it can handel the road, if you want to use it for gigs.
The Cleans are lovely. It takes pedals with no problem.
Gain channel is good, and many rock/metal players will have fun with it. But I would stick a TS (TubeScreamer) in there, somewhere.
Send/return is handy. footswitchable. No level control for it.
20 watt or 10(ish) watt-mode. Big pro, because 20 watts of tube amp is still a lot of LOUD. Lower power mode is much more workable in a home studio situation. The 20 watt's can carry you in band practice or even a live situation. This is not a bedroom practice amp :) ...
The Tone-shift. Metal players of a certain style will love this: it cuts the mids in a very metal like way, (mid-scoop).
The con's.
The Tone-shift. Great for metal, not so great for anything else. Make sure it is not engaged the first time you try it, or it will confuse you ;) .
Reverb. It has it, but it feels more like a selling point than actual effort to put a good, usable reverb in. It is vage, or in your face. No or little inbetween.
It is a very beefy sounding amp. If you are looking for a bedroom or living room tube/valve practice amp, this one is mostly likely too loud for that, even in lower power (10 watt-ish). This is NOT a bedroom practice amp. look at the 1 or 5 watt for that. Really. I mean it. :)
For those who like to mod their gear, I do think this amp would like a V30 or greenback a little better than the Seventy-80 that comes with it. But the Seventy-80 does what is asked of it.
This is a very good amp, great tones of it's own, and takes pedals and fx well. It will take whatever you throw at it, and make it louder, with no issues.