The ATH-M50 after the years that it's been on the market is still one of the best headphones for the price*, unless you really don't like a balanced sound signature. Yeah, the highs measure kinda uneven but the peak (in the mid-treble) and the dip (in the lower treble) are pretty narrow and not that high in amplitude. Personally, it's not enough for me to bother with EQing. I use a FiiO E07K amp/DAC though, so your sound (and your ears) may vary. I remember plugging the M50 straight into my iPod and the treble imbalance was noticeable. "S" sounds and some cymbals/hihats sounded too sharp. The sound is definitely smoother with the E07K. The bass is maybe a couple decibels above what is considered neutral, and the mids are as flat as can be.
To the OP - the highs are definitely not shrill or screaming, though if you're listening out of an iPod or most computers/laptops the aforementioned treble imbalance might bother you. Also, the highs sound smoother after a short break-in period.
*I am assuming a price of $100. MSRP is $159 but it's possible to get the M50 for $100. soundprofessionals.com often puts the M50 on sale. At $159 the M50 has a bit more competition, especially when some $200+ headphones are on sale.