HubSpot has been doing this successfully for a while now. When you sign up for the free marketing and sales tools, you get immediate value from the product. But, as you get more value from the free product, they tempt you with free-trial landing pages for blocked features. This allows the user to experience the new feature for a limited amount of time before upgrading. For HubSpot’s sales team, it’s also convenient: It acts as a “hand raiser” to cue them to reach out and ensure the user succeeds with the new feature.
