That reviewer probably was comparing them to cans that hype the highs and lows, with an exaggerated scoop to the mids (like most consumer headphones). Mo Fis are more like studio reference monitors where they are designed to give you exactly what you put into them. I don't find them at all lacking in highs or lows, they are very, very balanced, and as Shasha pointed out the mids are outstanding. More detail and dimension than any headphones I've ever tried.
I've been listening to mixes I've done and heard things I didn't know were there before, such as elements in a layered synth sound that are buried with other phones. The bass has a clarity that made one of the tracks I recorded with my old bass player sound so good that I almost called him to tell him I never realized how good he played. Every note rang out like I'd never actually heard it before.
For monitoring the Axe-FX II they are the first headphones I've used that really sound right. I've never been satisfied with my high-gain tones through headphones at all. They just never sounded like they do through my studio monitors or XiTone cabs, and while they don't sound exactly the same now, it is pretty close... and definitely a lot better than with my AT M50's, Sony 7506's and whatever model of Sennheiser phones I have laying around.
So, yeah, go for it. I was pretty skeptical about them myself until I tried them. Now I'm really glad I did.