I have had this one and a FitBit, both for a little over a year, and have to say I prefer the FitBit.
As someone else said, the Soleus is not so comfortable on your wrist. I found myself having to take it off any time I had to type on a keyboard or do something that required resting my wrist on a level surface. Which, of course, leads to forgetting to put it back on, which eventually makes it useless for using it as a tracker.
It syncs and charges via USB with the cable Soleus provides, but the connection is not well designed, making it hard to connect properly and maintain the connection. It slips off the two little ports too easily and is difficult to align and secure.
I was also super annoyed with the Go! buzzing on my wrist every time my phone was buzzing in my pocket with a message or call. I set up the Bluetooth connection to use the iOS app for looking at my data, but the default seems to be that it will also notify you of calls/msgs. I did not know that and it took me a while to figure out how to turn it off. The annoying vibration felt like those obnoxious buzzer things people use when pranking a handshake. Imagine sitting at your computer at work, productively typing away on something and the Go! regularly jolts you with a hard buzz on a wrist that is already sore from wearing the thing. Multiply that by all the apps for which you forgot to turn off notifications, and you get the picture.
Sleep tracking was good, but my habit at night is to remove any watches or wristbands and allow the skin on my wrist to breathe overnight. Since I have a memory foam mattress, setting it beside me in the bed to monitor motion for sleep cycles wasn’t an option, either.
The biggest advantage of the comparable FitBit over this device is that you can use it without the wristband and simply clip it to your pocket. The docking interface is more secure, and the app and online interface are better designed, too.
If you don’t want to spend $100 for the FitBit, this might be for you, but I’d advise waiting for the price to come down much more, or buy a $5 pedometer and track your own data in one of the zillions of free apps and sites out there that already do a great job of monitoring data for calories, nutrition, exercise, sleep, and more.