They're not awful, with an OK source. The tuning is a tad warm, and the subsonics aren't impressive- so stuff that goes down low won't be as impressive as (say) the HE-560. However, what bass is there, mostly midbass, is snappy. Upper mids (high strings etc.) suffer a bit of suckout- almost all headphones seem to (though the HD650 and Utopia do OK here). Staging is so-so, and depends a bit on the amplifier, but it's not all that horrible for an inexpensive Planar.
Attacks are fast and snappy, pizzicato is a joy. Danse De La Fée Dragée will sound delicious. The last movement of Bruckner's 5th.. a bit less impressive.
They nice for the money, and definitely a different flavour to the HD650. They're not perfect, of course, so there's an element of personal preference in play too.