I've been interested in activity trackers for a while and got a MS Band v1 pretty early on. Over the past year MS has been releasing more SDK/API access, which has been great to see:
http://blogs.msdn.com/b/visualstudio/archive/2015/07/15/micr...One thing to note is that while the SDK (Win/iOS/Android) provides full sensor access, it's stream access, which requires constant connection w/o auto-reconnects for subscriptions. Sadly, there's no access to sync the device in the way that the MS phone apps do - getting rollups requires using the MS Health Cloud API, which is post sync/upload.
Overall I've been pretty happy with my Band (I got a warranty replacement after the screen started fritzing out a few months ago for no apparent reason), but I'll be holding off on the Band 2 (and looking closely at the new Garmin Vivosmart HR) for a couple main reasons:
* Battery life - my #1 complaint w/ the Band, still unsolved w/ v2. I'm able to sleep comfortably w/ my Band v1, but w/ about 1.5 days of battery life, it means it's always dying if I even forget to charge once. Once I do charge it I'll often-times forget it when going out, or it doesn't get fully charged and dies while I'm out and about, so in practice that means that I have it on me and charged maybe half the time. (by comparison, the Vivosmart HR claims 5d battery life)
* Waterproofing - the Band is still IPX67 while many other devices like the Garmins are 5ATM+ - this makes a huge difference in the scenarios of when you have to take the device off.
Some other thoughts:
* All the sensors are great and very few (if any devices) have anything close, but I've yet to see even a graph of the GSR measurements, much less get anything useful/actionable from it. The UV sensor is similarly pointless. Despite less sensors, other companies are doing some seemingly more useful things with their devices. (vo2max estimates, pulse oximetry, etc)
* You can change the time/time zone w/o an Internet connection - I fly and travel a lot and this was actually a huge problem w/ my Basis Fitness Watch, so I'm really happy that the Band fixed this very early on.
* I primarily have my Band synced to my iOS device, and I've had to reset/repair/resync the BT multiple times, but that seems about par for the course for all the devices I've used.
* One nice thing is w/ the v2 is that they fixed the charger placement - on the v1, it's on the inside of the device and basically leaves a indentation/welt in your arm and just generally was uncomfortable. Dunno how/why that ever got past any sort of product review. That and an OLED/wakeable display are good improvements, but don't make for a compelling $250 upgrade.