It does sound really good. I have a Takamine EN-10C (original 90s version) and a Martin 000-15M too.
The Martin 000-15M sounds marvellous and clearly better than the Takamine (which does sound good) but the D28MD that arrived today annihilates the tone of 000-15M; the difference is profound. Not only does it ring with harmonics on all played notes but its dynamic range is astonishing; it'll play quietly or thrash it a bit and it goes LOUD but never distorts! I bought an inexpensive Fender 12 string recently (£350) and that has NO dynamic range at all; one volume and obvious distortion if you exceed it!
However; this is my 3rd D28MD (see the context of this thread) and they've all been different.
The first was brighter than the next 2, the most dynamics, 25 second sustain and was tough to play. The 2nd was tonally less bright, less dynamics, more balanced but only sustained for 10 seconds and was easy to play. The 3rd has the sweetest tone, amazing harmonics and a 15 second sustain and is quite easy to play with good dynamics. I think I did well eventually.
What I'm saying here is that if you ever intend to purchase then try a few, Covid-19 permitting.
By the way ... the Modern Deluxe version of the D28 is not a standard D28; it's got a titanium truss-rod, carbon-fibre bridge plate (ebony bridge), compound radius neck, waverly tuners, maple binding and "liquid metal" bridge pins. It's the D28 enhanced. Love it.
Thank you all for your kindness and support during the last few days; it helped raise my spirits. Cheers from England guys.