I bought and sold the T51p, the sound and fit wasn't to my liking....; the build quality and pads though were exceptional. I read many reviews about T51p and DT1350, I noticed the DT1350 had a facelift version, great, purchase made. In my opinion the 1350 is better looking than the T51 and the only negative would be 1350 stock pads. As soon as I swapped out the pads to T51p comfort and sound improved.
My somewhat initial impressions are, muddy bass and sibilant treble. I'm trying to hear clean mids but they're drowned out by bloom in the bass and splashy treble. How much (if any) burn-in is required?
I am not a fan of these either, in fact I've just returned a pair. I should say that these were only used for portability/commute (on the tube and flights), both of which these cans failed to impress. Also, the headband was uncomfortable after an hour or so. Not all bad, the build quality seems top notch.