So I've looked around with searches and checked the FAQ so if this is already covered I apologize.

Is 2.1 a drop-in replacement for 2.0.1?

I found out we are using 2.0.1 and I need to use query_cache'ing so we need to upgrade. If I can just drop in 2.1 that would be great. (And where can one download old versions of the jar files?) Thanks!

-eric

Older versions are here:
http://prdownloads.sourceforge.net/hibe ... &sort=desc

as for compliance.... just run your acceptance and unit tests against your application and you will know for sure. If you do not have them then it is very good time to create them :)