Jalapeño is a tool to abstract your developer from the persistence layer in a Caché database. Hibernate is a tool to abstract your developer from the persistence layer in a (general) relational database. Comparing these two is a bit like comparing apples and oranges...
Object databases are a good choice for a limited set of applications, relational databases are a good choice for a broader set of applications (and give you *way* more opportunity to shoot yourself in the foot).
No matter what "abstraction" tool you choose, if you choose the wrong persistence model, you'll be in a world of pain.
Ultimately, *ANY* tool that keeps your developer from understanding how data is persisted is a tool that will only cause grief at scale. The more abstracted the persistence, the bigger pain in solving the inevitable problems.
Nay, give me a human developer with a brain on his shoulder and some actual experience building large-scale systems. That person can do code reviews and teach solid techniques.
Spend more time up-front in development, spend less time "post-release" chasing fires. Sadly, deadline-driven development doesn't accept this.