How important is win/loss/churn research data to your overall KPIs? What percentage of your overall data comes from w/l?

It's incredibly important! Not just the individual win/loss/churn reports, but aggregate data as well can be a foundation or validation for decision making. 

In past roles I've used this data to focus programs around:

• Competitive Intelligence - This one is obvious, but one key output has been more intense focus around how to win against specific competitors.
• Content - Hearing why some prospects chose a competitor and the picture they paint can be exteremly useful. It shoudl spur ideas for positioning, and content alike. But historically I've used it to fuel blog posts, webinars, and different content for products that have directly impacted new sales, and retention.
• Product Adoption - If you know a competitor is talking specifically about an aspect of your product, ensure you drive adoption (assuming it's core to your product and helps retain customers). 

Win/loss data can be a great source of competitive intel. Obviously it is ideal if you have the budget for a third-party to do some win/loss interviews or secret shopping, but even if you only leverage in house resources, win/loss analysis is huge. Most companies do track their overall win rates against competitors as part of their quarterly or annual KPIs. While we all know that those metrics are sometimes suspect due to inaccurate entry or inaccurate info, they are usually at least directionally correct. I do track win rates as part of my overall product marketing dashboard but I use a rolling 3 or 6 month window to try to minimize data issues or seasonality.

I don't have a specific percentage to share in terms of how much of overall competitive intel comes from win/loss data but I do use win/loss interviews to validate competitive intel I want to double check like features they have or don't have, pricing, what messaging they are using etc. It is helpful to use win/loss info to confirm things you already suspect or that you've read about on their website or in other sources like analyst evals. As you probably know, vendors sometimes stretch the truth and so win/loss info can be good ways to try to confirm competitive intel!