The PX 210 BT headphones are charged over a micro-USB cable, the port for which is hidden under a small flap on the left earcup. Sennheiser quotes 12 hours of battery life, we managed to get about 10. The discrepancy is likely a result of our having to keep them at full volume the whole time when using an iPod. Even then they weren't particularly loud - at least our hearing is safe though.
The right earcup has controls on its outside. The track forwards/backwards and play/pause buttons will work with any AVRCP-compatible player with which headphones are paired, while the volume buttons control the PX 210 BTs directly. This is worth noting as with our iPod touch we had to adjust both volumes to get decently audible sound.
What's good to note is that there's a tangible difference between using standard A2DP Bluetooth and apt-X. Indeed switching between Bluetooth with apt-X and the provided cable, there wasn't any noticeable difference in quality, suggesting that the codec is doing its job properly.
The audio quality isn't what we'd call stellar, but it's still pretty good. There's good clarity, with vocals coming across well and a nice warm base, but the high end is a bit lacking in definition for our tastes. Without using an apt-X adaptor the results are less good, with noticeable compression on some tracks, but it's still listenable.
Inevitably a similarly priced pair of non-Bluetooth headphones won’t struggle to best the PX 210 BTs. But, and the 'but' is important, once you get used to listening to your headphones, unimpeded by cables you really won't want to go back to a pair of tethered cans - especially now the use of Bluetooth doesn't necessarily mean degraded audio quality.
There's something slightly incongruous about Bluetooth headphones that actually sound good, but the PX 210 BT wireless headphones manage it. You'll have to factor in the cost of an apt-X adaptor on top of the headphones themselves to get the best out of them, though.