User adoption is crucial for SaaS businesses as it helps in decreasing customer churn, increasing retention rates, boosting lifetime value, enhancing acquisition, activations, and signups to paid plan conversions. Effective user adoption strategies include continuous onboarding, pushing activations and "aha!" moments forward, personalizing the onboarding experience, providing accessible support and training, and finding the right balance of friction in product usage. Measuring user adoption success can be done through customer churn cohort analysis, A/B testing, microsurveys, tracking signups to paid plan conversions, and monitoring Net Promoter Score (NPS).