Synced (or should that be sunk) easily with my iPhone. Very light. Took a few goes to work out how the earpiece fitted in my ear, but have gone a few hours now, and I'd hardly know I was wearing it. Calls are clear and it looks okay, if a little plasticky.
On the downside, the controls aren't very intuitive so you'll definitely need to read the manual. It is only three pages but I'm a bloke and we don't do manuals so I now feel like I need to put an Ikea shelf unit up without looking at the instructions to prove myself again.
There are only two buttons to control power, call answering and volume, but that's down to its size, so I think that's an acceptable tradeoff. The charger also uses a non-standard USB connector which is why I marked it down one star as I've already got a drawer full of proprietary leads and could really to with manufacturers sticking to standard sizes. On the plus side again, the idea of a charging carrying case is a great one, so while you're carrying it around while it's not in use, you're also recharging the battery.
I've not had it long enough to say anything definitive about battery life, but my initial impression is very good, overall.
===Update===
I've been using the earpiece for a few weeks now and have to say that the idea of having the carrying case function as a charger is inspired. By charging the battery in this, and then making sure you store the earpiece in it between uses means the effective battery life between charges is considerably extended in normal use (by normal use, I mean that I don't have it in my ear and switched on constantly, but rather use for a couple of hours while driving and then put away afterwards).
The non-standard USB connector still niggles, though. I either have to carry the lead around with me, or buy a lead for each additional device I might want to charge from.