I had been using several pairs of HD662F, each one lasting well more than a year before breaking down (one of the speakers muting thanks to shabby wiring), and decided to test these ones since they were a new entry in the 662 line.
The reasons I liked 662F were clear, balanced sound and good muffling, and while the muffling was good even with the new streamlined headband design, the sound wasn't exactly what I was looking for; instead of a more neutral response with controlled bass, it had hissing trebles and rumbling bass. Some reviews said to cover some of the inner speaker holes with tape for better sound, but it didn't really help and fiddling with it felt like a waste of time. Eventually I got used to the sound, but I still missed the previous clarity of ).
Only after few months of use, the new detachable cord jack with its flexible tip started to loose up. Going out for a trip (which I rarely did with the old 662 designs since they have a solid 2,5 meter cable; this one came with both 1 m and 3 m cables) ended up being the finishing blow and once again I found myself with the other speaker dead. Compared to all the previous 662Fs, this pair lasted only few months (consisting of 99% desk use and extremely rare "mobile" use).
Afterwards I decided to invest more for a pair of AKG K-271 MKII (K-271 being the design that Superlux plagiated for their old 662 line), and the moment I put them on I felt the familiar clear & neutral sound of 662F (without any unneeded fiddling) and as a bonus they were extremely comfortable to wear (less pressure on my big head and big ears without any significant compromise in muffling), so I definitely recommend getting them over any Superlux 662 version if you take your audio seriously.