I'm a huge W5000 enthusiast. In my opinion, they are essentially the creme de la creme of audio technica headphones. Bad fit issues are usually sorted out with a bit of bending of the top bars and wearing in, and almost all people who find the stock W5000's sound undesirable would find the sound of the F5005 more to their liking.
The stock W5000's have a wonderful soundstage and are perfect for classical music. Personally I prefer to listen to acoustic on them. The details in the mids and highs are immaculate and the bass is subtle and smooth. People find these mids and highs somewhat aggressive, and they have the tendency to fatigue your ears.
The F5005 mod calms down the aggressiveness in the highs and mids and makes long term listening much more feasible. It also encourages more bass and brings the soundstage a little more closer and forward.
I highly recommend the cans for their ability to pick out details and enjoy your music, their comfort and looks.. You can feel the buzz of the stringed instruments it's simply wonderful.
They're not the best all around cans though, although the F5005 mod helps a little with this. The bass is emphasized, and I wouldn't consider these "fun" cans by any means. These are sit down, close your eyes, and immerse yourself phones.
Also: Im always frightened of scratching the wood.