It appears my search for decent wireless headphones continues but these are the best I've found (aside from some issues which may or may not be a trouble for you).
First off, unlike some (most) wireless headphones that I've tried these do actually sound very good. In fact I've got a pair of wired B&W P5's and I reckon these might sound better, they have a very clear sound. That is providing you don't use the noise cancelling option which unfortunately ruins the sound completely. Not just "a little bit" but worse than the free headphones you get with your phone. Not quite sure who at Sennheiser listened to them in this mode and thought "that's good enough". It hollows and thins out the sound terribly. Who cares if the noise cancelling works when it sounds this bad. Ug. The headphones themselves without noise cancelling do actually get rid of some background noise but I've yet to try them on a flight where I'm sure the roar will seep through.
As my Galaxy Note 2 supports Apt-x then I can only comment using this and it exhibits little (if any) of the normal "Bluetooth" (ie. hard and compressed) sound. They sound suitably "hi-fi" with over Bluetooth and via the cable. Very listenable and engaging. No complaints at all here.
Build quality is "adequate" at best and they are not a particularly good looking pair of headphones. Considering the price I'm sure materials could have been better, they are quite plasticy and not very "premium". Having said that they are also light and extremely comfortable to wear.
A caveat others have flagged is that they don't go very loud, in fact they struggle to go "loud" at all. On cable only then you run them at full wack and still wish for more volume. They are a little louder via Bluetooth (when I'm guessing an amplifier is kicking in) but I've still had to use the Pre-Amp setting on my media player to boost the level a little and it starts to sound a little "coarse" at max volume (from both headphone and phone even when pre-amp is set flat).
So, there you go. If you don't mind about/need noise cancelling and (I am assuming) have an Apt-X compatible device then these sound good and are very comfortable for long periods. For the money however I would expect noise cancelling not to affect the sound at all and for the build/looks to be better. Have decided to send them back...