Latest data from Reliance Jio suggests 350 min/month usage for the initial subscriber base is quite comparable to the usage of incumbents. Now switching data usage to a new connection is reasonably painless (e.g., tethering) and the high usage reported by RJio is not much of a surprise.
But voice usage tends to be sticky, with factors like good coverage and MNP / change of numbers preventing easy switching (especially with the higher end customer base). The usage number reported suggests that for a large number of the early adopters into Jio's network, the Jio SIM has become the primary SIM. This could imply decent acceptance of Jio's voice product (one of the perceived weak points in the company's strategy).
Jio has tied up with Samsung for bundled Jio connection (three-month unlimited free data and voice), which so far was available only with Reliance's Lyf branded phones.