I am looking for innovative ways to gather feedback from customers of a platform and a service in a global scale. Although I am willing to talk with users, I am more interested to know if you have any advice in how I can do it unobtrusively. I am thinking in something where the customer actually don't need to spend a lot of energy and time and I get data with quality. Any software or thoughts that pop up in your mind?
I think there is no substitute for getting your product in front of real people as early in the lifecycle of the product as possible. While I understand the desire for quantitative data, if the product is not yet released, then that option is not available. Ideally you will get your product in front of people who are your customers, or at least who are as much like your customers as possible. Going to the mall or a coffee shop with a laptop and getting into conversations with folks who don't mind talking to you can teach you a lot in just a few hours, even if you only get 10 people to view your product and give you feedback. The time for getting lots of user data is later when the product is available. The suggestion of getting feedback from internal folks within the organization is also a great option, although I assume moves farther away from your customer and carries with it some assumptions your customers may not have such as familiarity with your product or service.
You can try to place a button 'Review Us' near their screens, and ensure your polls are very flexible to have customer enter their ideas, their thought.
One more thing, you can try to use a live chat during beta period to reach customer very closely.
Sometimes the most subtle way of getting the user feedback is by using analytics. Of course this will not give you valuable feedback right away, you need to put in the right tracking in the right places then be able to read it. I often find that this data is more reliable than user giving direct feedback. It's easier to understand the user needs than the wants.
I have found some good products like feedbackerr.com, usabila, usertesting.com and there are others out there. You ultimately will be paying users for their feedback. I think this is a better approach than asking users to 'donate' their time and tell you their opinion. This approach doesn't properly value their time or their opinion- and will result in low-quality information.