They (Instant Apps) will almost certainly fragment our users experience - iOS vs Android. Come on, we've been there with Flash and ActiveX to name two. HTML5 makes most of what Instant Apps are about obsolete.
Instead, I wish Android offered better distribution or apps update channels for normal apps as I'm really disliking the Google Play. My users often don't see any update for weeks. I switched to Fdroid and it's a pleasure but unfortunately there are no unattended updates (unless rooted) and requires initial setup on the users part.
So, Google please fix Google Apps instead or even better, support alternative repositories with automatic apps updates after user grants permission.