As with most other models of Bluetooth headphones I've encountered, pairing your smartphone, tablet, or other Bluetooth-enabled device with the WP-450s is easy enough, though you'll run into an occasional snafu. Also, expect to have some dropouts now and again; that's par for the course for Bluetooth, which has a range of about 30 feet.
Like the WP-350 pair, the WP-450s sound quite decent for Bluetooth headphones. They offer decent clarity and deliver a good amount of bass and also play loud. I was expecting a little bit more because they cost close to twice as much as their step-down sibling. Their sound seemed a little pumped up, which some people may like, but I thought the WP-350s were a little warmer and easier to listen to over longer periods.
In going wireless with Bluetooth headphones, you usually have to give up some sound quality because Bluetooth compresses your music and has a tendency to flatten out fidelity. You'll experience some of that with these headphones, although they do feature the aptX codec, which is supposed to improve sound quality. The iPhone 4S doesn't support aptX (both the headphones and the device you're streaming from have to support aptX), but I did try the headphones with the Samsung Galaxy S3. In listening to standard MP3s, I didn't really notice a difference. I then ran some lossless tracks though the headphones and noticed a slight improvement, but I wouldn't say these headphones are good enough to really deliver a refined listening experience. Creative's own $99 Aurvana Live headphones sound significantly better and are more comfortable, but that's a wired over-the-ear model (sorry for the apples-to-oranges comparison, but I thought it worth mentioning).
While I wasn't blown away by the sound, I thought the WP-450s sounded better than a lot of in-ear Bluetooth headphones I've tested and delivered similar sound quality to the pricier AKG K830BT headphones (also an on-ear model). I also thought they were superior to a pair of JayBird Wireless SB2TR Sportsband Bluetooth headphones I had in-house.
As far as using the WP-450 as a headset for making calls, it seemed to perform a bit better than the WP-350 model. You can hear callers quite well but because the microphone is housed in the right earcup, it's a little far from your mouth. My test callers said my voice slightly muffled but was "fine" overall. They could hear me, I just didn't come across entirely clearly. (Note that I was indoors, not outside.)
Finally, battery life is rated at around 8 hours on a single charge, which is a standard spec for Bluetooth headsets. I was able to use them for 5 days straight on my daily commute without having to recharge, and I travel a little less than 2 hours a day.
Since I liked Creative's WP-350 Bluetooth headphones, I naturally assumed I'd like the step-up WP-450s even more. However, that didn't prove to the be the case.
I did like the WP-450s and they're comparatively good Bluetooth headphones, though I didn't feel they offered much of an advantage over the WP-350s, whether in terms of sound quality, comfort, or build quality.
Overall, the WP-450s' sound is a bit beefier than the WP-350s', you get a tighter seal with them, and they seem sturdier overall. But I found the WP-350s more pleasant to listen to and a little more comfortable. In other words, the WP-450s are solid Bluetooth headphones but I can't recommend you run out and buy them over the WP-350s, which I consider a better deal overall.