Conversation on some of the other threads has converged on the fact that yeah, it's a 1st gen device so it's quirky and less than ideal (e.g., reliability of HR monitoring). You might add to that, many of us (I'm assuming) keep our devices 1 or 2 years and then replace them. So whether to buy or not now feels like a tough choice mainly because they're hard to find. Once the 2nd gen is leaked/announced, nobody will want a 1st gen, like (again, I'm assuming) nobody wants a 1st gen Surface. Take away the scarcity and I would probably recommend waiting another 3-4 months for more news. But then I should add that I have a bad case of device envy and so would feel like a total piece of crap if I bought a Band tomorrow and the 2nd gen were announced soon after. If you can keep your hands over your ears and not get distracted by tech news, @Davd_Lohrentz is right, it's an awesome device.
As far as helping motivate workouts, there is a great honeymoon effect with the Band which lasts about a month -- after that, it's you, your running shoes (or bike), and the road. If it's not in your heart to stick with a fitness plan, the Band joins the treadmill, elliptical, and weight bench that are already in the basement, coated in a light layer of dust. Actually that's not 100% true -- the non-health functions (e.g., text/email notifications) still make it worth the price of admission.
Lastly, as an Android owner I have to say I'm scratching my head a bit at the discussion of NT, WP8, kernels, etc. From where I'm sitting the Band OS is pretty much a non-issue. It's true that I don't have Cortana and so don't have voice input (or the keyboard, darn!), but otherwise my user experience with the Band is pretty much the same as any WinPhone or IPhone owner. Not sure how much any upcoming changes to the OS/kernel enter into the decision-making.
-Matt