I have never been a headphone fan, nor have ever considered buying Sennheiser, because I couldn't afford the more expensive models.
I have already owned the following headphones:
Audiotechnica ATH-M30x - Nice quality but there was an annoying frequency gap. Probably I have had a faulty unit, because I have listened to the ATH-M20x and they sounded absolutely acceptable.
Audiotechnica ATH-M50x - Nice quality but at that price point I don't expect such a disco sound.
Philips SHP-9500 - so bright that my years almost started bleeding. Don't understand why it is so praised in internet.
Beyerdynamic DT 770 Pro 80 Ohm - Amazing quality. The most cute and comfortable headphones I have ever had! Unfortunately, quite demanding towards the source. The high frequencies are a bit sharp to me, especially when the source is poor. Otherwise, a great professional tool!
AKG K171 mkII - very decent headphones. As many AKG headphones, it lacks a bit of low end to me. Not very comfortable but has a very pleasant sound. I enjoyed it a lot!
AKG K240 mkII - It also lacks depth in the low end. Has a bit boomy and echoing sound to me. Material quality is no match with the others, but it is durable and at that price it is a very nice allrounder.
AKG K271 mkII - decent headphones. Sounded to me as a mixture of the above two. Sound wise, the K171 mkII are superior than the K271 and K240, but the last two are more comfortable in my opinion.
I was really tired of headphones with recessed mids (cheap commercial tricks), lack of depth, dryness, frequency gaps, sharp high frequency peaks, impedance issues and etc.
Unfortunately didn't find what I was looking for, so I bought a Sennheiser HD 280 Pro half an year ago from pure curiosity.
I also found them strange looking at first glance as many people do.
Sound wise, the HD 280 Pro is the best headphone I have ever listened to.
Never felt such pleasure from listening to the music, even on decent stereo speakers and much more expensive headphones than the listed above. I often realize that it is 04:00 o'clock in the morning, but never get tired of listening.
Sound is so balanced, full bodied, with natural timbre, warmth and all it's beauty that makes listening to all kinds of music and sources an endless pleasure...
Very universal headphone - sounds great on every source I have connected it to.
In a world where marketing has replaced quality long ago, I didn't really expect to find such a great product.