Whew, glad to hear this!
I have migrated all reports built in Google Looker from using earlier connector versions to 1.4.0. All reports working as expected. I did have a small glitch in a handful of reports when a metric in a column chart switched from the metric I was using to something else. I don’t have screenshots, but the switched metric was either a calculated field from Piwik Pro or a calculated field from Looker.
Yeah, it’s possible. There was quite a lot of fixes to the dimension/metric schema since v1.0.7.