Pros: Fairly Detailed, Plenty of Bass
Cons: Ear cushions
I have used the Sony MDR-7506s as long as I can remember. I do Front-of-House (FOH) mixing for bands, and these phones have been by my side for many years.
Some people hate the cable, i like it, and I haven't ever seen one fail. These headphones have an enjoyable sound, decent clarity and detail (occasionally can be a little fatiguing), and a solid bass presence. The bass isn't always the most clear (something I find with many closed over-ear headphones, until you spend more). The upper-mids seem a little recessed for me, but not to the point of being too laid back. I also notice that these headphones can get a bit sloppy with busier songs.
While you can technically run these straight from your favorite Apple/Android/Computing device, you won't get the best from them (they'll likely sound dull and thin). These definitely come alive with a decent headphone amp.
If there is one thing I recommend for anyone considering these, get better ear pads. Personally, I bought the Beyerdynamic EDT250V pads. So much more enjoyable.
All that said, for a headphone that's been around since 1991, it holds it's own against current competitors at this price point. If you're looking to stay under $100, you can do a lot worse than these.