As very inexperienced in headphones my view of the DT250-80 is heavily colored by the fact that I just bought them. Beware. For what it is worth then: the first impression in the store, coming through PA2v2, was like "hey, no annoying bumps in the frequency response to be found anywhere, great!". A quick listening with samples from the extremely different types of music I like closed the deal for me, these are allrounders of very high standards. Slightly to the warm side as said before, I don't mind at all. I used to crank up the bass with the Koss portapro, with DT250 I have no reason to have it any other way than line-out straight through PA2v2. Full, rich, smooth.
They can handle a great variety of music with ease, and they give subjectively "the same" spectral balance to me regardless of listening volume. Sometimes I like to listen at really low sound levels, sometimes I like to crank it up until I feel the impact from the drums in the chair, transmitted through my arteries throughout my body from the ears... I feel completely safe with the DT250-80, no ear-piercing effects happened like with the DT770-250 which was my prime candidate. DT250 feels extremely clean, almost to the point og being boring at first. No bells and whistles. Maybe the DT770-250 had less burn-in than the DT250, or maybe the PA2v2 was not as good of a match here. Never mind, the DT250 play what is there to play, be it clean punchy bass notes from a kick-bass or complex harmonies from a grand organ. Great smoothness in the mids and highs to my untrained ears, great vocals and treble extension without any sign of exaggeration.
The soundstage is perhaps not the greatest there is but in my mind many "better" cans in this respect create the impression of a larger soundstage artificially through an uneven frequency response that becomes just fatiguing to me after a while. My ears are allergic to marked bumps in the spectrum, especially in the upper mids and lower treble so that kind of tricks are not for me.
With DT250 I cannot stop listening, much louder than I should just because they are so clean. I'm now enjoying Rammstein's Rosenrot album for the first time, crystal crear brutality straight from my son's collection. An interesting thing with good gear is how they manage to reproduce intentionally distorted sound, also here the DT250 show off with professional precision. I just realized their lyrics suck rather hard though... never cared to listen before but now it is difficult to ignore.
You asked for impressions, these are mine. Probably I'm just trying to justify my purchase so you should not listen to me at all...
Honestly you really should listen for yourself, with your gear and your music. If I had based my purchase on reviews only I would have ordered DT770, and would probably rave just as much over the investment.
