Pros: Build quality, punchy bass, detail
Cons: Possibly long-term comfort
Basically these are the best £80 I've spent in ages. Coming from a pair of CX300 II's the difference really is night and day, where the Sennheiser's were all undefined mushy bass that drowned everything else, the bass in these Yamaha's is really tight, accurate and punchy. It's powerful but very controlled, so it doesn't cover the rest of the music.
It's a really enjoyable sound, the balance is exactly what I wanted: you get lots of detail and good separation, the treble isn't harsh and the mids are nice and smooth.
They also seem really well built, the aluminium housings are nice and solid and they have a reassuring weight to them.
Would definitely recommend.