I've had mine since its been out, and here's my opinions.
1. Features, its probably the most feature rich "smart watch" out there at the 199 price point. I put the term smart watch in quotes because in some ways, its not a full fledged smart watch. Its more geared to active folks, those who would have bought a fitbit.
2. Battery, lasts about 1.5 days, I find I need to charge it more often now then when I first bought it.
3. The band/shape of the phone. Its not great and you really do need to wear it with the display on the inside of the wrist. Doing that means it will be a scratch magnet and you absolutely need the screen protector. I was very careful with it, just it has a fair number of scuffs.I eventually got the screen protector so that damage has been mitigated.
4. GPS, more often then not, I have trouble locking onto the GPS, so much so, I'm going to bring it back for a possible replacement. When I first got it, I had no problem with the GPS. Now it fails more then it succeeds with the GPS lock. There's no rhyme or reason, weather/location etc. Some days it works other days it doesn't.
5.Step accuracy. It seems a little generous in measuring your steps. Not by a lot but it does seem a little high for what I do.
6. Run accuracy without the GPS. I'm amazed at how accurate it is. They did a good job with that. I run a set route, and so I knew my mileage before and it was pretty close measuring my run.
7. The iOS app - It always wants the location services on and it drains my battery. I had to disabled location services for the app. Not sure why it kept reading my location even when I quit the app.
Overall, I give MS a C-. Earlier, it would have been a B and maybe if I get a replacement to deal with the GPS issue, it will go back up that.
I'm planning on buying the Fitbit Surge which is due out in early 2015. This has all the features of the Band but it appears to be a better product.