Softube became the official software side of Marshall a few years ago. They made the code for their digital amps and later released amp emulations only for the UAD platform (can only be used with UAD soundcards). The demo's I listened at the time were great but never had a chance to try them myself, after that totally forgot about it. Seems they not too long ago went native.
Few days ago a total Marshall fan friend of mine send me some sound clips for preparation to his next single, to be honest if I didn't know probably would be mistaken they were recorded in a studio. It was a softube Jubileee he got on discount and to me these guys have done everything right.
The gain stages has the dirt we love, the cab. section mic.ing sound very authentic, they even placed a room sound and they are controlled by a mini-console. So the workflow is just like how its done in the studio. You don't need the amp room plug-in (their amplitube sort of solution) to run the amps, but the amps don't come with pedals etc. so you'll need other plug-ins to support it if you go that route.
Just a final note; Its a very convincing amp sim. so this also means don't expect loads of gain (aside kerry king model) , ultra smooth tone etc. out of the box. I saw 1-2 youtube vid.s some getting good metal tones but I'd say look elsewhere for easier solutions (Neural, THU...), this is aimed more for the guys who're into classic Marshall sound.