In my experience yes. It is especially clear on more limited (ARM) devices (Chromebook ARM, Atom/Celeron laptops) though; if you get stuff running at all, it is very slow; swap Oracle JDK in and it's suddenly very usable. I myself don't do a lot with server side Java anymore, but my colleagues tell me the same things, but it's fast enough for most applications there. On the client it's far more obvious.