Is it feasible (and when yes, could it be advisable) to complete queries of Hibernate-planned data without needing SQL-strings, however, many OOP way rather?

make use of the Criteria API, more good examples here.

I'm using linq. But HQL uses organizations, so it ought to be named object-oriented :)

It is possible using Criteria, however i think the queries are usually more understandable when utilizing HQL with parameters. Still, Criteria works well for that queries which are quite dynamic (I have seen people concatenate HQL strings for dynamic queries, and Criteria is cleaner in individuals cases).