Let's get one thing straight..if you've bought a Marshall you'll not be wanting to play 'Oh My Darling' at the local tea-dance! This amp is NOT designed to be everything to everyone, but ALL MARSHALLS to everyone. I'd say this is like having a Marshall museum in one room! Go in, pick your sound and use it. The OD1 channel is deceptive one. It doesn't have the bite of OD2, but play a humbucker shod guitar on the neck PU and it has a stunning lead tone, great for the Gary Moore/ Pete Green sort of thing. If you want more modern stuff, just switch onto OD2, scoop out the Mid to about -2 (yup!) leave the Bass and High on 3 or 4 and shred!!! There's 26 factory preset's one of which is bound to suit your basic sound (try preset 10!! - pure Rock!) and then modify it to taste! On the clean side (boo! hiss!) there's enough useful sounds but it's not where this amp's forte lies.
Even with a humbucker equipped guitar (Patrick Eggle Berlin Pro) this will still hum if you get a bit close to it at high gain settings, but as it's a rack why should it even be on the stage?
I've never had any trouble with Marshall gear, but that's not to say I'm 100% sure of everything I use! I take a DRP-1 preamp with me just in case to rehearsal AND gigs (straight into the desk in emergencies!) I'd like to think the JMP-1 will be no different. It's very rugged, nothing sticks out too far and it looks well built. I'll keep you posted.
I've lusted after one of these for ages and I'm really pleased with it but it's what I wnated. The ADA didn't have quite the same sound, and the Boogie Triaxis was 3 times the price...not 2 times the amp. In my rig (9100 power amp and Rocktron Intellifex Ltd) it's the business. I'd like to get a spare but can't afford it. I wish that there was a rear input, so i don;t have to run a lead from my Nady into the front but that's a minor gripe. If you love Marshall, you've GOT to get one