What a shame that it doesn't quite do either of these things perfectly!
With regards to the car, it connects fine and the controls are easy enough to learn. There is also an Android app to help, but you can't program the main function when using the headset in car. For me, the best function would be for it to perform a Google Now search, as I can ask it to do anything (much like Siri on iPhone) but instead it will only go to the Voice Dialler (which limits me to dialling numbers) or S Voice (which is not very useful). This is a huge oversight by Jawbone that you cant program this, or use the app to change the default. There are work-arounds but they're not simple or for novice smartphone users. Another problem is how LOUD it is when using some functions. Even if you adjust the volume down on some things (e.g. in a call) other updates will scream down your ear (such as the battery level update)
Now for the problems with PC. I run Windows 8.1 and the 10 preview. It doesn't play nice with either of these Operating systems - it will pair and seem to connect, but the disconnects and will not work until removed and re-paired again. Very disappointing and again, something that Jawbone could have easily implemented as I have older Bluetooth headsets that work seamlessly for this function.
Wouldn't be fair if I didn't point out the plus-sides too:
Noise cancellation is amazingly good - often even clearer than when speaking directly on my phone in a silent room
Battery lasts around 6 hours which is pretty good if you are driving a lot in a day (as I do)
You are provided with a tiny Micro USB charging cable, very useful if you have USB charger in your car (as I do!) to keep the battery topped up
Changeable voices are hilarious and fun!
Status light makes it easy to see what the device is doing
It's very small and discreet
I can only hope that Jawbone will address the 2 or 3 bad points above in a future update, then it will be the PERFECT bluetooth headset!