Best to post this to the ActiveJDBC community: https://groups.google.com/forum/#!forum/activejdbc-group, I can only speak for myself.
We started using ActiveJDBC in 2009. Currently we have it powering 4 websites for a major insurance company (3 environments for each: test, qa, production), massive batch processing architecture clustered with Weblogic JMS (ten nodes), and a handful of internal projects. We do not use Hibernate anymore, except legacy apps.
Our DB is all Oracle (legacy DB) and our schema is pretty complex, with links to other schemas, sequences, triggers, etc. Current schema size is 90 tables. I have seen other people on ActiveJDBC forums use it on schemas of several hundred tables.