learning Hibernate

I have assumed that it would be good to learn Hibernate, mostly because 
I've seen many job ads in which Hibernate was listed among the desired 
skills.

So I've been working at it.  I've run a few very simple applications. 
I've read a lot of online documentation and half of the book _Hibernate 
In Action_.

It is difficult.  Hibernate does not relieve the developer of the 
requirement to understand relational databases and SQL.  Rather it adds 
to what the developer must know.  And it appears to be quite a lot to 
know.  At this stage I would say that learning Hibernate (after one has 
learned relational databases and SQL) is more work than learning 
relational databases and SQL.

To use Hibernate successfully it seems that one needs to learn to think 
in the Hibernate way, and you can't do that until you've "grown up" in a 
Hibernate world.

At this point I am still assuming that Hibernate must be a great tool, 
because so many employers ask for it.

But I have some doubt because, in a parallel development, for years now 
many job descriptions have asked for experience with EJB.  But does that 
prove that EJB is a good technology, or only that lots of people have 
been caught up in EJB hype?  EJB seems to be losing some if its glamor 
in what I'm reading recently, and I am given doubt that EJB has ever 
lived up to its promises.  For all I know the enthusiasm over Hibernate 
may follow the same pattern.

See, I used the word "pattern".  Now hire me.

But, if all this leads up to a question, are there people who are using 
Hibernate successfully in real, working, mission-critical, applications? 
  Probably that is a dumb question.  But still it would encourage me to 
receive an affirmative answer from respectable people on this list whom 
I know.

Thank you,
Rich Hammer