Ok, so I'll weigh in.
I think what most of the people have said so far is mostly correct. The main reason for Marshall's "Diversification" into JMD and MA is price point and competition. Marshall is having a hard time competing with Line6, etc. in the lower-price-range. Your average buyer will take a Line6 over
a Marshall MG on sound/price unless they're just buying name. AND... they're ignoring all the great things all the modders are out there doing. I think most players would pay $300 more for a KILLER sounding JVM with MM/Heyboer transformers instead of the current product. You go cheap, you get cheap, you sound cheap. Simple.
As far as the higher end, it's component-based. You can take a JVM and put a set of Heyboer or MM transformers in it and improve the sound tremendously. Upgrade some capacitors here, resistors there, and now it sounds like you want (and you've just become a "modder").
Most people equate the "downfall" of the great Marshall tone with the switch to Chinese transformers around the Mid-JCM900 era. I look at the OT in my Hughes & Kettner TriAmp MK II in relation to the OT in
my JVM410H and the H & K is about 150% the size of the JVM. (No replacement for displacement?)
Regarding the HAZE 40, I believe it's the most misunderstood amp out there right now. I'm doing an official gear review on one including a head-to-head with the DSL401 at the moment (I'll post the link when it's completed). The Marshall HAZE 40 is intended to capture the 70's tone. More importantly, it is NOT a high-gain amp. It'll do crunch at best, and some of the best crunch is actually achieved by diming the Normal channel. Don't slam an amp for not being something it was never intended to be. You don't slam a JC-120 because you can't plug straight in and play Slayer. I think the thing that throws people about the HAZE 40 is the tube complement--just because it is a Marshall and has three ECC83's and two EL34's that doesn't make it a Plexi. The tone on the HAZE 40 is there--it's got good tone, but it's not a Metal amp. Also, inevitably, the digital FX section is going to color the tone as well. I'd expect to see some HAZE mods emerging over the next several months. If the HAZE 40 had gain on tap, it'd be close to the perfect little gigging combo. Good effects, but not over the top, plenty of tone, and plenty of gain. However, that would change the intent of the amp. If you want more gain out of a HAZE, throw a pedal in front (just like you do with every other amp that you feel needs it).
Bottom line, unless Marshall pulls its head out of the sand, realizes it's losing the tone wars, and makes the necessary adjustments, they won't be around too much longer. When you can purchase a Splawn QuickRod for $1850, there's no reason to buy a Marshall JVM2 at $1499 ($1599 if you buy the "shrouded in mystery"
JVM210HCF model, whatever the "CF" designates).
Cheers,