I got 2 pairs from FutureShop yesterday for $100. After ~24hrs of burn in, here's my impression:
I usually use either my ES3X customs or CK100, so I will base my impression off of those headphones.
Fit: Comfortable for me using medium tips. Deep insertion into the ear sounds reduces the soundstage, and increases the bass quantity. Shallow insertion produces a more spacious sound, but there is slight increase in sibilance and more treble sparkle.
Treble: It's not as sibilant as I've read, and the treble extends well and is indeed very crisp.
Mids: I'd prefer a lil more forward mids, but it's generally nicely balanced with the treble. Vocals are rich and smooth which is great for jazz.
Bass: My biggest complaint, I find the bass quantity to be too much, making these phones bottom heavy and often overshadows the mids and treble. However, the texture of the bass is great and can really go very deep.
Soundstage: Quite narrow compared to ES3X and Ck100, but I know it's not fair comparison. Soundstage has good depth and instrument separation is great.
I think the FXT90 can almost rival the IE8; they are very dynamic and fun to listen to, especially for rock. The biggest strength of this phone is the timbre and natural sound of instruments, making music very believable (something CK100 isn't good at). At this price they're definitely a bargain!
I'll keep burning them for a couple of days and hope the amount of bass will decrease...