Eugen Beyer invented the concept and first ever headphone set back in the 1930's, so this is a company that knows what they're doing.
It's no coincidence that Beyer's DT100's have been almost the defacto ubiquitous headphones seen in daily use in pro recording studios and in TV/broadcast/film work for a long time. The headphones are comfortable to wear over long periods, very snug fitting and the phones are a fully closed back design - which means that ambient sounds from outside the headphones are kept out and sounds from the headphones are kept in - so they won't leak/spill out into your recordings if you're recording a vocal or up close dialogue track for example..... oh, and they sound good too.
Now - the DT150's are of a very similar clunky 'Dr. Who cyberman' design, though not quite identical - ugly plasticky angular brutes cosmetically really - but the DT150's do have an extended frequency range over the DT100's which makes them better suited to mixing and general tracking duties, and that's why they're more often seen on the heads of producers than the DT100's - although it's clear that they're also good for the same duties you might expect to use DT100's for - ie monitoring primary recording with microphones. I'd say that they could even be used for mix mastering at a pinch in such situations where perhaps you simply cannot use studio loudspeakers for the task. They do take a bit of time to 'break in' from new - then the bass response is pretty good, perhaps just a tad shy of truly full bass range sound whilst the mid range is quite pronounced and clear (perhaps lifting slightly in the human voice/mid speaking frequency range) with a generally smooth and rounded high end, not at all harsh and shrill as you can find in a lot of other headphones. You'd be hard pressed and have to spend a LOT more money to get a bit more performance than these tough, functional and ergonomic workhorse headphones offer sound wise.
Being designed for the busy working professional environment, all parts can be got at short notice from pro audio outlets and field replaced in seconds individually should anything break or wear out........ but really - these headphones are as tough as old boots and can be relied upon for years of faithful service.
As I said earlier, it's no coincidence that you see these headphones in use a LOT in pro audio situations. They work. And they work well.