We have tested 'thin' jdbc driver in Oracle Instant Client 10 
(http://www.oracle.com/technology/tech/oci/instantclient/instantclient.
html), and it works very well with Hibernate and clobs.
Our test application use a oracle database table with clobs in it and 
use 'text' in the hibernate map file, 'String' in POJO class. with 
this jdbc we need not change any code, just use set() method to set 
the Strings (clobs) then use session.save() to save the object. With 
this driver, we can even use hibernate.jdbc.batch_size=20. I think 
it's the best solution for clobs in Hibernate.