Tired of having to untangle my iPhone earphones every time I take them out of my bag, I decided to try going wireless with a pair of Bluetooth headphones. I initially bought the Creative WP350 but found them a very strange size - they are "on-ear" headphones but are not large enough to cover your ears fully (and I think I have average-sized ears) and so feel like they are constantly going to come off. After sending them back, I've struck gold with the Philips SHB9100/00.
Initially, I was looking for a small-ish pair of headphones, or at least one that folds up neatly to better fit in my work bag. The Philips doesn't do that (though the phones do rotate sideways which makes it a lot easier to slip inside a bag) and while the photos make the headphones look quite big, I'd describe them as medium-sized - bigger than the Creative WP350 "on-ear" style but smaller than the full-sized over-ear cups you see on some really heavy duty headphones. For me, it's perfect - I don't have the feeling that they're falling off or not big enough as I did with the WP350s (and indeed far less sound leakage as a result) but they aren't too big - the cups are cushioned and feel very comfortable.
In terms of sound quality, a lot has been said about this already below. I'm no audiophile, but even I can recognise the difference between my iPhone earbuds and these - the sound quality is very impressive, especially for something which is connecting via Bluetooth and is powered by a battery.
The Bluetooth connectivity has so far been brilliant - very easy to pair with my iPhone 4S and hasn't lost connection yet.
All in all, an excellent purchase - these headphones have great sound quality, feel very comfortable and look expensive and stylish, and provide exactly the sort of wire-free commute I was looking for.