To avoid any duplication of features, we no longer support the Snooze functionality that was built into Streak. Any email threads you snoozed with Streak will remain that way, though, and resurface as expected. You can access these threads in a folder in the left navigation bar titled Snoozed by Streak.
Gmail's snooze option requires Conversation View to be on (which we also recommend for Streak).
If you're familiar with our old feature, the Snooze Only If No One Replies option is now the default for Gmail's snooze. If there's a reply, the email will be un-Snoozed and return to inbox.