People (including Ubuntu/Debian) seem to think that openJDK is just a bit slower and "less polished" but a fine drop in replacement. It has been my experience there is lot's of stuff it still just doesn't support. The saddest and most obvious was last time I was helping a first year comp sci student they couldn't even do lab #1 in it since openjdk didn't have the fancy new output writers. Sure you "don't need" them, and a bunch of other things it's missing, but those missing things quickly add up and start spelling lots of software that openJDK cannot run. And also first year comp sci students can't even use it for school.

It is not a drop in replacement that is a bit slower, it is incomplete and I'm tired of people not understanding this. There are things it cannot do and software it cannot run.