Here are my findings:
My Opera browser is currently pointing to IcedTea 1.2.1 according to about : plugins which I believe is OpenJDK7.
My wife loves playing canasta on Yahoo games (she would NOT let me have PC-BSD without this) and it works good.
time.gov runs a Java applet and that works. This is how I sync my watch to the atomic time so it's very critical to me.
So far I've tried code that I compiled in OpenJDK6, jEdit, NetBeans & IntelliJ IDE and it all works great. It even looks better and runs faster!
So I'd say this one is a success.