We currently have _many_ issues open related to our db layer  . Do
you think that Zend_DB will be a better fit? Zend_DB also seems to
have SQLite support, which is interesting for me from two reasons:
- ability to bootstrap Mantis using just a Java servlet container (
using Resin's Caucho and ZendDB's SQLite support );
- much easier management for integration tests, which allows us to
easily 'swap' the database content when needed.
with them it is quite easy to interconnect to the supported DBs. It's also should be quite easy to use your preferred DB locally or run unit tests against various DBs (did not try this yet...)