I don't know why so many are focusing on a number. That isn't what will cause it to flourish or fail, it is simple things like:
1) Being able to opt out of creating an account local or otherwise, always online, Bing, store, and cloud integration upon install. If people do not want to do things, you do not handcuff them to it to force them. They found this out the hard way with xbox one. Having the ability to opt out of features when installing has always been a well appreciated windows install feature not something they need to mess with when it comes to maintaining your consumer base. Some people just want a streamlined, secure operating system, without the fluff not a one size fits all multimedia device. Allow customers to easily choose what they want and how they want to use it.
2) Familiar UI, controls, storage and monitoring. Some people want things to be where they expect to look for them and when they are not there, that is an irritation not an innovation. It is kinda like having the idea to change how a steering wheel works on a car. If suddenly turning it right makes it go left and turning it left makes it go right, people are not going to see that as an innovation, they are going to not buy the car that does that. Different does not mean better. Always having the option to have a classic view, nothing on your desktop if you so choose, and being able to access your controls and files in a familiar manner are things that may be over looked by designers.
My dad, for example, has had multiple strokes and had to re learn how to speak and understand words and his computer is his lifeline to be able communicate and live a somewhat normal life. When they do something as simple as change how you access a file, or how a button looks and where it is located it makes doing things extremely difficult for him because he is unable to learn new information easily, nor is he able to remember that it happened the next time he logs in. It is a repeated daily frustration for him when they do something as simple as change the look of his email. They always need to retain the ability to access things in a familiar manner to accommodate all who use them, and not worry about trying to be " new and different" or many will not change because of how difficult it is for them and how much longer it takes them to accomplish anything. For many elderly like my parents or the disabled changing these things makes their lives much more complicated than just " look you access this way now" and they should realize that those changes can be a determining factor as to whether or not someone buys their product at all.
3) Not thoroughly checking the stability, security, and functionality of the product before releasing it. Worrying more about deadlines than the quality of product you are releasing never goes for a good release of a product. Yes, people will notice, and yes people will judge your product by this.