Purely as an engineer, there's just one relatively minor point. Having started as a small startup back in 2005, there are definitely remnants of a bygone era of "wild west coding" at Etsy. New code that gets churned out nowadays is honestly fine, but it's not entirely rare to come across a codebase that has a lot of legacy code in it still.
With some of the shakeups in the past half a year (As of November '17), there've also been some re-orgs and while it was overall positive and a great change in my opinion, naturally there are still some kinks to be worked out.
That said, I want to keep it clear that the above two points are actively being worked on, at least within the teams I interact with. They're just points to keep in mind given recent events.